Orgány imunitního systému Poruchy imunity Imunodeficity Hypersensitivita Alergie Autoimunita Fyziologické použití imunitního systému genetika (MHC aj. lokusy) invaze a rekognice cizorodého stimulace zevními faktory během vývoje imunitního systému (tj. prodělané infekce, (ne)hygiena, ATB, vakcinace aj.) ba kterie |nádorové buňk' cizorodé buňky a tkáně (vč transplantace) účelná imunitní reakce obnovení původního stavu Tonsils and adenoids Thymus Lymph nodes Appendix Bone marrow Lymph nodes Lymphatic vessels Spleen Peyer's patches Lymph nodes Lymphatic vessels Patologická aktivita imunitního systému genetika patologická reaktivita vůči ZEVNÍM antigenům, které by normálně měly být tolerovány patologická stimulace zevními faktory (senzibilizace alergeny, virová infekce, aj.) patologická reaktivita vůči VLASTNÍM antigenům, které by normálně měly být tolerovány alergie autoimunitní nemoci Hypersenzitivní reakce (Coombs & Gell) Typel Type II Type III Type IV Immune reactant "gE IgG IgG TH1 cells TH2 cells CTL Antigen Soluble antigen Cell- or matrix-associated antigen Cell-surface receptor Soluble antigen Soluble antigen Soluble antigen Cell-associated antigen Effector mechanism Mast-cell activation Complement, FcR+ cells (phagocytes, NK cells) Antibody alters signaling Complement, phagocytes Macrophage activation IgE production, eosinophil activation, mastocytosis Cytotoxicity \m m m »J &<^ V Ag ir platelets P+ % complement & immune complex bloodJ vessel vyr >"? complement IFI^^S^1 v €^ IL-5 ^eotaxin Mr % chemokines, cytokines, cytotoxins w CytOtOxinS, inflammatory mediators Example of hypersensitivity reaction Allergic rhinitis, asthma, systemic anaphylaxis Some drug allergies (e.g. penicillin) Chronic urticaria (antibody against FCeRIa) Serum sickness, Arthus reaction Contact dermatitis, tu berculin reaction Chronic asthma, chronic allergic rhinitis Graft rejection Figure 13-1 I m m u no biology, 7ed. Klasifikace poruch imunity • imunodeficity - problém nespecifické (fagocytóza, komplement) nebo specifické imunity (T či B lymfocyty, protilátky) • primární, Vrozené (detailněji viz Imunologie) — genetika • sekundární, získané — nemoci GIT (malabsorpce), ledvin (nefrotický sy), kostní dřeně (aplasie, leukémie), výživy (kachexie), nádory, infekce (AIDS),.... • hypersenzitivní reakce - výhradně záležitost specifické (adaptivní) imunity!!! - alergie (mechanizmus viz Resp. systém - astma bronchiale) - autoimunitní nemoci deft PRINCIPY IMUNITNÍ TOLERANCE (AUTOTOLERANCE) Imunitní tolerance vs. autoimunita a autoimunitní nemoci autoimunita = imunitní reaktivita proti vlastním antigenům („self" antigény) - původní představa • autoimunita = nežádoucí fenomén („horror autotoxicus", Paul Ehrlich) - ale ve skutečnosti běžný (nicméně klinicky němý) fenomén • prokazatelná existence autoreaktivních klonů T-lymfocytů - musí být tudíž zaručena tolerance vlastních nepoškozených buněk (self tolerance) na více úrovních • centrální • periferní autoimunitní choroby - detekovatelné morfologické a funkční poškození 75553019 Autoimunita je záležitostí adaptivní (specifické) imunity!!! 0 Erythrocytes ôryiŕi-oeyto progenitor , Natur* Reviews | Immunology Jak se dosahuje diverzity receptoru lymfocytů (B a T) Heavy chain L V OJ T lymfocyt Somatická rekombinace - B lym - v kostní dřeni - T-lymf vthymu vede k produkci obrovského množství náhodných variant vč. těch autoreaktivních Chromosome 14 Jax6i C ß-chain locus Chromosome 7 T VRX52 ] Dpi Jßirf Cßi Dß2 Jß2«7 Cß2 Molekulární mechanizmy centrální imunotolerance • B &T lymfocyty mají původ v kostní dřeni • pozitivní a negativní selekce upravuje jejich repertoár — B lymf. maturují a jsou selektovány v „bone marrow" — T lymf. maturují a jsou selektovány v thymu • tudíž většina autoreaktevních lymfocytů je centrálně odstraněna (apoptóza) neboje anergická Surface immunoglobulin or B-cell receptor antigen-binding site light chain Antibody T-cell receptor antigen-binding site transmembrane region heavy chain variable regions constant regions transmembrane region a chain p chain Figure 3.1 The Immune System. 3ed. {'(> Garland Science 2009) Centrální a periferní tolerance B lymfocytů možnosti v případě autoreaktivity - apoptóza - receptor editing protože stimulace B lymfocytů periferně vyžaduje spolupráci T lymf., jejich tolerance musí být kontrolována důsledněji Central tolerance (bone marrow) Peripheral tolerance (lymphoid organ: spleen, lymph node) Follicle \ 1 Anergy | 1 Follicular exclusion | \ JApoptosis 1 Elsevier. Abbas et a): Cellular and Molecular Immunology 6e - i / lung uiyiiius jhearf^y Thymus Cortex Medulla Hassalls corpuscle Figure 7-8 part 1 0f2 Immunobiology, 6/e. (© Garland Science 2005) Centrální tolerance T lymfocytů - thymus T-cell precursors travel from the bone marrow to develop In the thymus Mature T cells leave the thymus and travel to secondary lymphoid tissues Immature CD3"4"8" double-negative thymocytes o Immature CD3*4'6( double-positive thymocytes O * #V Mature CD4+S and CD8*4 ^ thymocytes _j diferenciace a zároveň selekce T-cell precursor rearranges Its T-cell receptor genes in Ihe thymus Immature T cells that recognize sell MHC receive signals tor survival. Those that Interact strongly with self antigen are removed if urn the repertoire T-cell progenitors develop in the bone marrow and migrate lo Ihe Ihymus Posilive and negative selection in Ihe Ihymus Princip of centrální tolerance - maturace thymocytů From Bone Marrow Thymic Medulla immature thymocytes from the bone marrow undergo T-cell receptor (TCR) rearrangement stage 1: once immature CD4+8+ thymocytes enter the thymus they undergo MHC restriction, whereby only CD4+8+ thymocytes that interact with MHC-presented antigen on epithelial cells receive a positive survival signal - those that do not interact are deleted by apoptosis. stage 2: this stage involves the negative selection of thymocytes that survive stage 1. Thymocytes with too strong an association for self-MHC and self-antigens are deleted by apoptosis, allowing the remaining thymocytes to mature into CD4+ T-helper (Th) cells or CD8+ cytotoxic (Tc) cells Role MHC v selekci T lymfocytů Human HLA complex Exogenous antigenic peptide Exogenous antigenic pBptide -:nds within groove binds wjth1n groove Cytoplasmic tall Complex HLA MHC class II III I Region DP DQ DR C4, C2. BF B C A Gene products DP aß DQ aß DR aß c protein* TNF-a TNF-ß MIAU III AC III \ \ Peptide generation & loading on MHC z cytoplazmy (např. virové) proteazom (+IFNy) kratší délky z ednozomu (např. extracelulární fagocytované) lyzozomální proteázy delší délky Infected cell Antigen^ fragment Microbe Class i MHC molecule T cell receptor QAntigen associates with MHC molecule ©T cell recognizes combination (a) Cytotoxic T cell (b) Antigen-presenting cell Antigen fragment Class II MHC molecule T cell receptor "Helper T cell Selekce T lymfocytů v thymu je podmíněna afinitou jejich TCR k antigenům/ peptidům MHC II Ř 0 c 1 0 > S? I ow Peripheral T tell Affinity repertoire threshold Death by neglect 1 1 / Positive selection Negative (apoptosis) / (survival and selection / differentiation) (apoptosis) Intermediate Affinity of TCR-peptide-MHC interaction High Nature Reviews | immunology Thymus °>8 o°o°g° oo OOOix °o0°o0 cro O o o° oo0 °§o°oo Negative selection: cloral deletion receptor editing anergy_ ooO°nr o oQo°' Lymph node Affinity Agonist selection: Tn«,oelte C-Mäna- lELs NKT eels Provide immune responses to foreign antigens °OOoo. o o0 o oo0o0 oooo o °o° O Q_ Regulate immune responses Copyright © 2C05 Natura Publishing Group Nature Reviews | Immunology Quantitative perspective The affinity of the T-cell receptor (TCR) for self-peptide-MHC ligands is the crucial parameter that drives developmental outcome in the thymus. — Progenitors that have no affinity or very low affinity die by neglect. This is thought to be the fate of most thymocytes. — If the TCR has a low affinity for self-peptide-MHC, then the progenitor survives and differentiates, a process that is known as positive selection. — If the progenitor has a high affinity for self-peptide-MHC, then several outcomes are possible. • First, the progenitor can be selected against, a process that is known as negative selection. The main mechanism of negative selection is clonal deletion, but receptor editing and anergy have also been described. • Second, there seem to be mechanisms that select for high-affinity self-reactive cells and result in differentiation into a 'regitlatory'-cell phenotype. It is not known what determines whether a T cell is tolerized by negative selection or is selected to become a regulatory T cell- • (IEL, intestinal epithelial lymphocyte; NKT cell, natural killer T cell; TReg cell, CD4*CD25* regulatory T cell). Thymus opouštějí kompetentní ale „naivní" T lymfocyty, které ale musí být aktivovány v periferii Mature T cells encounter foreign antigens in the peripheral lymphoid organs and are activated Activated T cells proliferate and migrate into peripheral sites to eliminate infection Mature T cells migrate to the peripheral lymphoid organs Activated T cells migrate to sites of infection Figure 7-2 part 2 of 2 Immunobiolagy, 6/e. (© Garland Science 2005) Normální aktivace T lymfocytů T cells enter lymph node across high endothelial venules in the cortex T cells monitor antigen presented by macrophages and dendritic cells T cells that do not encounter specific antigen leave lymph node through lymphatics T cells that encounter specific antigen proliferate and differentiate to effector cells ^7 Figure 8-4 Immunobioiogy, 6/e. (© Garland Science 2005) An important part of determining which signalling molecules are present is the local environment within the architecture of the immune system = i.e. the inflammatory environment shapes the activation of both T cells and APCs Infections tend to cause inflammation and the release of inflammatory cytokine molecules like interferon-gamma, and find their way into the immune system via the lymph system to the lymph-nodes. Therefore the lymph-node is specialized for presenting/ore/gn antigens to generate immune responses. Normální aktivace Th lymfocytů T-lymphocyte / Antigen Presenting Cell Interaction Molecules 'Adhesion' Molecules LFA-1.CD2 CD4.CD8 LFA-3.ICAM-1 CD28, Biete. bttrleukins 1-12 Interferons Tumour necrosis factors etc etc. T-lymphocytes express a CD4, a receptor for the MHC-class II molecule antigens from the infectious organism or foreign tissue are processed into peptides by APCs (B cells, Mac, and DCs) and these peptides that bind to the MHC-II molecules that are recognised by the T-lymphocyte using its antigen receptor - MHC restriction A number of other adhesion molecules and growth factors are also used to send signals between the T- lymphocyte and the APCs, and only if all the signals are correct does the T-lymphocyte become activated and aggressive — an aggressive response results in the multiplication of that clone of T-lymphocytes, which also develop the ability to kill all further infected cells, using a similar recognition process to that shown above Aktivace Th lymfocytů na „lokálním • outside the immune system many of the important molecules for signaling aggression are not expressed • In this situation, although antigen can still be recognized by the T-lymphocyte, the response is not one of aggression, but rather of tolerance • This non-inflammatory environment can be reinforced by the presence of antiinflammatory cytokines like IL-4 and IL-10, that can either be produced by healthy tissues, or by a population of T-lymphocytes that are protective and tend to yet further suppress any tendency to (self) aggression tedy zásadně závisí prostředí" "Non-self : activation Professional Antigen Presentation fig. CD2S/B7 etc Inflammatory Environment fig. OTf- i , IL-2 etc Immunological tissues eg lymph-nodes "Self' ; tolerance Non-inflammatory Environment «£. IH. 10. TW ttL Normal self tissues eg. pancreatic islets Aktivace T lymfocytů vede k jejich proliferaci ve funkčně různorodé efektorové buňky CD8T cells: peptide + MHC class I Cytotoxic (killer) T cells cytotoxins Cytotoxic effector molecules Perforin Granzymes G ranu lysin Fas Ugand Others IFN-7 TNF-ß TNF-a CD4Tcells: peptide + MHC class II TH1 cells cytokines macrophage Macrophage-activating effector molecules IFN-7 GM-CSF TNF-a CD40 ligand Fas ligand Others IL-3 TNF-ß (IL-2) CXCL2 (GROß) cytokines B-cell activating effector molecules IL-4 IL-5 11-15 CD40 ligand Others IL-3 GM-CSF IL-10 TGF-ß CCL11 (eotaxin) CCL17(TARC) Figure 8-31 Immunobioiogy,6/e. (© Garland Science 2005) Funkce T lymf. (CD4/CD8) se liší primárně podle jejich cytokinového profilu Cytokine Effects on Effect of gene knockout B cells T cells Macrophages Hematopoietic cells Other somatic cells lnterleukin-2 (IL-2) Naive, Tn1, some CD8 Stimulates growth and J-chain synthesis Growth - Stimulates NK cell growth - i T-cell responses IBD Interferon-7 (IFN-y) TH1, CTL Differentiation lgG2a synthesis (mouse) Inhibits TH2 cell growth Activation, t MHC class I and class II Activates NK cells Antiviral | MHC class I and class II Susceptible to mycobacteria, some viruses Lymphotoxin (LT, TNF-ß) TH1, some CTL Inhibits Kills Activates, induces NO production Activates neutrophils Kills fibroblasts and tumor cells Absence of lymph nodes Disorganized spleen Figure 8-32 part 1 of 3 mmunobiology, ( /e.(© Garland Scie nee 2005) Cytokine Effects on Effect of gene knockout B cells T cells Macrophages Hematopoietic ceils Other somatic cells lnterleukin-4 (IL-4) Th2 Activation, growth lqG1. IgE TMHC class II induction Growth, survival Inhibits macrophage activation TGrowth of mast cells - No TH2 lnterleukin-5 (IL-5) TH2 Mouse: Differentiation IgA synthesis - - f Eosinophil growth and differentiation - Reduced eosinophilia lnterleukin-10 (IL-10) Th2, (human: some Th1) t MHC class II lnhibitsTH1 Inhibits cytokine release Co-stimulates mast cell growth - IBD Figure 8-32 part 2 of 3 Immunobiology, 6/e. (© Garland Science2005) Molekulárni mechanizmy periférni autotolerance • NEZBYTNÁ, CENTRÁLNÍ BY SAMA OSOBE NESTAČILA!!! - — it is not possible to express all self-antigens in thymus and ensure / the elimination of entire pool of auto-aggressive T lymphocytes / • (1) very low number of self-reactive lymphocytes (surviving the clonal deletion) escape the central mechanisms and leave the thymus — autoreactive B & T lymphocytes are normally present in healthy individuals • but in order to be activated they need many other signals, mainly from the innate immune cells - usually in the presence of infection or tissue damage • (2) intentional survival of autoreactive T cell differentiated into natural peripheral Treg to boost immune tolerarr6e^ — CD4+CD25+(about 5-10% of CD4 cells) — their development and maintenance is highly dependent on co-stimulation and IL-2 — Treg express CD25, TNFa receptor, CTLA-4, and Foxp3 — act in tissues to control inflammation via direct effects on effector T cells or DCs — suppression is contact and also cytokine dependent (TGF-b/IL-10) Self-reactive T cells are deleted in the thymus. Occasionally, self-reactive T cells may escape deletion In the periphery such escaped self-reactive T cells can cause tissue damage T cell specific for self antigen becomes a regulatory T cell (Treg) Cytokines (IL-10 and TGF-0) produced by Treg inhibit other self-reactive T cells Funkce T lymf. (CD4/CD8) se liší primárně podle jejich cytokinového profilu Cytokine T-cell source Effects on Effect of gene knockout B cells T cells Macrophages Hematopoietic cells Other somatic celts lnterleukin-3 (IL-3) TH1, TH2, some CTL - - - Growth factor for progenitor hematopoietic cells (multi-CSF) - - Tumor necrosis factor-a (TNF-a) TH1, someTH2, some CTL - - Activates, induces NO production - Activates microvascular endothelium Resistance to Gram -ve sepsis Granulocyte-macrophage colony-stimulating factor (GM-CSF) TH1,some TH2, some CTL Differentiation Inhibits growth ? Activation Differentiation to dendritic cells T Production of granulocytes and macrophages (myelopoiesis) and dendritic cells - - Transforming growth factor- (J (TGF-P) CD4 T cells Inhibits growth IgA switch factor Inhibits growth, promotes survival Inhibits activation Activates neutrophils Inhibits/ stimulates cell growth Death at -10 weeks Figure 8-32 part 3 of 3 Immunobiology,6/e.(© Garland Science 2005) Existují ještě další (CD25) subpopulace supresorových Treg lymfocytů které jsou inducibilní Thymic Selection 1. Positive Selection Low-Affinity self-ligandson thymic cortical epithelial cells 2. Negative Selection High-Affinity self-ligandson thymic medullary epithelial and BM-derived cells CDS* rogatory T c Under control of the AIRE protein, thymic medullary cells express tissue-specific proteins, deleting tissue-reactive T cells In the absence of AIRE, T cells reactive to tissue-specifc antigens mature and leave the thymus Figure 13-9 Immunobiology,6/e. (© Garland Science 2005) Genetické predispozice k autoimunitním nemocem silná (často monogenní) — skupina autoimunitních polyglandulárních syndromů • defekt AIRE = APS 1 (syn. APECED (autoimunní polyendokrinopatie -candidiasis - ektodermální dystrofie), Whitakerův syndrom) - M. Addison, + hypoparathyreoidismus, další • heterogenní genetický defekt = APS 2 (Schmidtův syndrom) — M. Addison, hypothyreoidismus, T1DM • defekt FoxP3 = IPEX (immune dysfunction, polyendocrinopathy, and enteropathy, X-linked) polygenní • MHCalely -> • jiné geny Associations of HLA serotype with susceptibility to autoimmune disease Disease HLA allele Relative risk Sex ratio (JrcD Ankylosing spondylitis B27 87.4 0.3 Acute anterior uveitis B27 10 <0.5 Goodpasture's syndrome DR2 15.9 ~1 Multiple sclerosis DR2 4.8 10 Graves' disease DR3 3.7 4-5 Myasthenia gravis DR3 2.5 -1 Systemic lupus erythematosus DR3 5.8 10-20 Type I insulin-dependent diabetes mellitus DR3/DR4 1 heterozygote | -25 -1 Rheumatoid arthritis DR4 4.2 3 Pemphigus vulgaris DR4 14.4 -1 Hashimoto's thyroiditis DR5 3.2 4-5 13-20 I m m u no bio logy, 6/e. (©Garland Sciente 2005) Endokrinopatie u APS 1 Environmental factors and activated innate immunity Příklady non-MHC genetických variant asociovaných s rizikem autoimunitních nemocí Gene Phenotype of mutant or knockout mouse Mechanism of failure of tolerance Human disease? AIRE Destruction of endocrine organs by antibodies, lymphocytes Failure of central tolerance Autoimmune polyendocrine syndrome (APS) C4 SUE Defective clearance of immune complexes: failure of B cell tolerance? SUE CTLA-4 Lymphoproliferation; T cell infiltrates in multiple organs, especially heart: lethal by 3-4 weeks Failure of anergy in CD4* T cells CTLA-4 polymorphisms associated with several autoimmune diseases Fas/FasL Anti-DNA and other autoantibodies: immune complex nephritis: arthritis: ly rr.phoprolife ration Defective deletion of anergic self-reactive B cells: reduced deletion of mature CD4* T cells Autoimmune lymphoproliferative syndrome (ALPS) FoxP3 Multi-organ lymphocytic infiltrates, wasting Deficiency of regulatory T eels IPEX IL-2: IL-2Ro/ß Inflammatory bowel disease: anti-erythrocyte and anti-DNA autoantibodies Defective development, survival or function of regulatory T colls None known SHP-1 Multiple autoantibodies Failure of negative regulation of B cells None known PTPN22 Increased lymphocyte proliferation, antibody production Reduced inhibition by tyrosine phosphatase? PTPN22 polymorphisms are associated with several autoimmune diseases Molecular mechanisms of abnormal B or T cell activation, i.e. autoimmunity (1) genetically determined failure of central or peripheral self-tolerance — strong or nearly monogenic determination • mutated AIRE (APS 1) = insufficient expression of tissue-specific antigens in v thymus • mutated FoxP3 (IPEX) = impaired differentiation of Treg • mutated Fas = defects of apoptosis (a thus negative selection) — moderate to weak genetic predisposition (2) mechanisms related to infection — production of proinflammatory/costimulatory signals — cross-reactivity (molecular and viral mimicry) • viral and non-viral peptides can mimic self-peptides and induce autoimmunity — polyclonal B cell activation by viruses and bacteria • typical for some bacteria and viruses (e.g. G- bacteria, CMV, EBV) inducing nonspecific polyclonal activation of B-lymphocytes (expressing IgM) in absence of Th-ly („by-pass oeffect") • if B cells reactive to self-peptides are activated, autoimmunity can occur (3) release of sequestered antigen (several sites of Jmmune privilege") — eye, testes , brain, uterus, ... (5) inappropriately high, abnormal MHC expression — e.g. type I diabetes: pancreatic B cells might express abnormally high levels of MHC I and MHC II upon the pathologic stimulation • MHC II - APC only! this may hypersensitize TH cells to B cell peptides Příklad (2): Role infekcí v rozvoji autoimunity Self-tolerance A ^ ■Resting" j cen ^tissue APC 0^ Self antigen Molecular mimicry 4 I Self-tolerance I APC expresses Microbe costimulatory Self-molecules reactive Activation ik, lT cell of APC Self antigen Self— B7 CD28 tissue Presentation of antigen by APC Autoimmunity Microbe Activation of T cells , Self-reactive T cell Microbial that rec0gnizes antigen microbial peptide Autoimmunity D Elsewiet. Abbas et at! Cellular and Molecular Immunology 6e - www.studentconsult.com Taken together - the most common postulated mechanism of autoimmunity Self-reactive lymphocytes n produkce prozánětových cytokinů a exprese kostimulačních molekul Activation of self-reactive lymphocytes Tissue injury: autoimmune disease Molekulární mimikry sequential or structural identity or similarity of microbe with host tissue — auto-aggressive reaction is mediated by the same effector mechanisms used for host defense against pathogen — however, often in the terrain of genetic predisposition • mainly MHC II alleles • but also MHC I-e.g. HLA B27 Associations of infection with immune-mediated tissue damage Infection HLA association Consequence Group A Streptococcus ? Rheumatic fever (carditis, polyarthritis) Chlamydia trachomatis HLA-B27 Reiter's syndrome (arthritis) Shigella flexneri, Salmonella typhimurium, Salmonella enteritidis, Yersinia enterocolitica, Campylobacter jejuni HLA-B27 Reactive arthritis Borrelia burgdorferi HLA-DR2, DR4 Chronic arthritis in Lyme disease Coxsackie A virus, Coxsackie B virus, echoviruses, rubella HLA-DQ2. HLA-DQ8 DR4 IDDM Figure 11-30 The In le System, 2/e (© Garland Science 2005) © Elsevier. Abbas et al: Cellular and Molecular Immunology 6e - www.studentconsult.com II A B I I HI- i MOLECULAR MIMICRY BETWEEN PROTEINS OF INFECTIOUS ORGANISMS AND HUMAN HOST PROTEINS KtsioW ScX^UtlKt1 • HtimAn LT1 lí r. I> E IE A ot D R E D L AttenAvirus 12 Ell) SM UM 1 K R G M ľ k ľ S Q C N l C Q G S í H ľ S 0 Q M Htinun inmngnndrfkicncy virus p2-l Human IjiG ronuant region IM) o y ■ t t t r i G V E T T T 1» S Mruln virus P.i Corticotropin U lf( L E C 1 k A L k L E C 1 H A C K • McjstťS vims P.t It «1 B 1 S D N L C o M C 1 5 F K LGQE "Invuih i'.nr. Hu liiKivui jf.-iťin i* Inh-J wviiid Ilk' if"Uin* iei ť*, b ju u ruw tnvn »In* n [»lUiil'iI iniiiiuinJoyK i í.h^-ivjkIi vir;» 'fcjxh iiumKr hlJiuUi iJw |-,iuIk>ci «n ihr kI.hi [»Mria t>I Ihť uiHruvU-iiiiiiuJ *o>u>> *.kJ u i ih«- luk.: : Aniiii- ■ .k hl rviÚMi* mv tiiJn.ih j t>v •iiiťK K ini •.■.sk'. iJi ii>H-tl rvMiluťt an; dii'W n m t>tiav. VHJW í AJ-i|ioí lfi*m MRA *H*hí autoimmune reaction (2- 3 wks) —>■ inflammation (T cells, macrophages) —>■ heart, skin, brain & joints Acute RF - acute inflammation — heart- pancarditis — skin - erythema marginatum — CNS - chorea minor (Sydenham) — migrating polyarthritis Chronic RF — deformities of heart valves • most commonly mitral stenosis Streptococcal cell wall stimulates antibody response plasma cell Some antibodies cross-react with heart tissue, causing rheumatic fever ie System, 2/e |© Garland Science 2005) Molecular mechanisms of abnormal B or T cell activation, i.e. autoimmunity • (1) genetically determined failure of central or peripheral self-tolerance — strong or nearly monogenic determination • mutated AIRE (APS 1) = insufficient expression of tissue-specific antigens in v thymus • mutated FoxP3 (IPEX) = impaired differentiation of Treg • mutated Fas = defects of apoptosis (a thus negative selection) — moderate to weak genetic predisposition • (2) mechanisms related to infection — cross-reactivity (molecular and viral mimicry) • viral and non-viral peptides can mimic self-peptides and induce autoimmunity — polyclonal B cell activation by viruses and bacteria • typical for some bacteria and viruses (e.g. G- bacteria, CMV, EBV) inducing nonspecific polyclonal activation of B-lymphocytes (expressing IgM) in absence of Th-ly („by-pass oeffect") • if B cells reactive to self-peptides are activated, autoimmunity can occur • (3) release of sequestered antigen (several sites of „immune privilege") — eye, testes , brain, uterus,... • (4) haptens becoming immunogenic • (5) inappropriately high, abnormal MHC expression — e.g. type I diabetes: pancreatic B cells might express abnormally high levels of MHC I and MHC II upon the pathologic stimulation • MHC II - APC only! this may hypersensitize TH cells to fl cell peptides Příklad (3): Ztráta „imunitní privilegovanosti" the original idea of „requested antigens" — auto-antigens separated from auto-reactive T-lymphocytes by anatomical barriers nowadays more of a functional concept of „immune priviledge" — anatomic factors — absence of lymphatics — absence of APCs — low expression of MHC I antigens — high concentration of antiinflammatory cytokines — high expression of FasL —» high activity of apoptosis of T lymph — etc. examples — eye —> sympathetic ophthalmia • against lens proteins (crystallin) — testes —> anti-sperm & orchitis — brain (BBB)—» antibodies in blood can attack myelin basic Protein if blood-brain barrier is breached — uterus (placenta) —» abortion — hair follicles —» alopecia trauma to one eye results in thfi release Of sčtfu Oslo red miraocjiar protein antigens \ 'š* FasL expression may play a role in "immune privilege" a Immune-privileged site: e.g. eye or reproductive organs Constitutive expression of FasL Activated inflammatory Tcell Immune-privileged tlSSUR I asL FasL expression in brain, eye, placenta, and reproductive organs is believed to contribute to immunological privilege Aberrant FasL expression may also be an adaptation of tumors to evade immune surveillance Apoptosis ot T cell The role of Fas ligand (FasL) in immune privilege Expert Reviews in Molecular Medcine©2001 Cambridge University P Molecular mechanisms of abnormal B or Tcell activation, i.e. autoimmunity (1) genetically determined failure of central or peripheral self-tolerance — strong or nearly monogenic determination • mutated AIRE (APS 1) = insufficient expression of tissue-specific antigens in v thymus • mutated FoxP3 (IPEX) = impaired differentiation of Treg • mutated Fas = defects of apoptosis (a thus negative selection) — moderate to weak genetic predisposition (see further) (2) mechanisms related to infection — cross-reactivity (molecular and viral mimicry) • viral and non-viral peptides can mimic self-peptides and induce autoimmunity — polyclonal B cell activation by viruses and bacteria • typical for some bacteria and viruses (e.g. G- bacteria, CMV, EBV) inducing nonspecific polyclonal activation of B-lymphocytes (expressing IgM) in absence of Th-ly („by-pass oeffect") • if B cells reactive to self-peptides are activated, autoimmunity can occur (3) release of sequestered antigen (several sites of „immune privilege") — eye, testes , brain, uterus, ... (4) haptens becoming immunogenic (5) inappropriately high, abnormal MHC expression e.g. type I diabetes: pancreatic B cells might express abnormally high levels of MHC I and MHC II upon the pathologic stimulation MHC II - APC only! this may hypersensitize TH cells to fl cell peptides Příklad (5): abnormální exprese antigénu MHC II. třídy v neimunitních bb. MHC II antigens are normally expressed only on certain cells!!! due to pathologic activation by proinflammatory cytokines (IFNy) this can change (MHC II are expressed together with tissue-specific Ag) auto-reactive T lymphocytes become activated examples — pancreas • [3 cells normally low MHC I expression, no MHCII • p cells in T1DM-high expression of MHC I and II - upon stimulation by infection? — similarly thyroid gla in autoimmune thyroiditis (Hashimoto) Thyroid cells do not normally express HLA class II molecules IFN-7 receptor thyroid epithelial cell IFN-7 produced during infection or nonspecific inflammation induces HLA class II expression on thyroid cells IFN-7 N/ HLA class II molecules I Activated T cells recognize thyroid peptides presented by HLA class II and induce autoimmune thyroid disease X7 Figure 11 -32 The Immune System, 2/e(© Garland Science 2005) autoimunita a principy etiopatogeneze autoimunitních nemocí Autoimunitní nemoci (AN) postihují cca 3 - 5% populace results from a failure or breakdown of the mechanisms normally responsible for maintaining self-tolerance in B cells, T cells, or both - nicméně patologická autoimunitní odpověď je obvykle cílena na omezené množství autoantigenů, která vede k poškozenítkání, je velmi specifická, většina imunitnítolerance zůstává zachována major factors that contribute to the development of autoimmunity are - genetic susceptibility - environmental triggers • such as infections , vitamin levels (vit. D), nutrition?, ... AN may be either - systemic - organ specific various effector mechanisms are responsible for tissue injury in different autoimmune diseases - (A) cell-mediated (hypersensitive reaction type IV) - (B) antibody-mediated (hypersensitivity type II, III, V) epitope spreading (progression and exacerbation of the disease ): - autoimmune reactions initiated against one self-antigen that injure tissues may result in the release and alterations of other tissue antigens, activation of lymphocytes specific for these other antigens Systémové vs. orgánově specifické AN Organ-specific autoimmune diseases Systemic autoimmune diseases Type 1 diabetes mellitus Rheumatoid arthritis Goodpasture's syndrome Scleroderma Multiple sclerosis Systemic lupus erythematosus Primary Sjogren's syndrome Polymyositis Graves' disease Hashimoto's thyroiditis Autoimmune pernicious anemia Autoimmune Addison's disease Vitiligo Myasthenia gravis Figure 13-1 lmmunobiology,6/e. (© Garland Science 2005) (A) Příklady buněčných (T-lymfocyty zprostředkovaných) AN Disease Specificity of pathogenic T cells Human disease Animal models Type 1 (insulin-dependent) diabetes mcllitus Islet cell antigens (insulin, glutamic acid decarboxylase, others) Yes: specificity of T cells not established NOD mouse. BB rat. transgenic mouse models Rheumatoid arthritis Unknown antigen in joint synovium Yes: specificity of T eels and role of antibody not established Collagen-induced arthritis, others Multiple sclerosis, experimental autoimmune encephalomyelitis Myelin basic protein, proteolipid protein Yes: T eels recognize myelin antigens EAE induced by immunization with CNS myelin antigens: TCR transgenic models Inflammatory bowel disease (Crohn's, ulcerative colitis) Unknown Yes Colitis induced by depletion of regulatory T eels, knockout of IL-10 Peripheral neuritis P2 protein of peripheral nerve myelin Guillain-Barre syndrome Induced by immunization with peripheral nerve myelin antigens Autoimmune myocarditis Myocardial proteins Yes (post-viral myocarditis): specificity of T cells not established Induced by immunization with myosin or infection by Coxsackie virus (B) Příklady AN zprostředkovaných tkáňově specifickými protilátkami Disease Target antigen Mechanisms of disease Clinicopathologic manifestations Autoimmune hemolytic anemia Erythrocyte membrane proteins (Rh blood group antigens. I antigen) Opsonization and phagocytosis of erythrocytes Hemolysis, anemia Autoimmune thrombocytopenic purpura Platelet membrane proteins (gpllb:IIla integrin) Opsonization and phagocytosis of platelets Bleeding Pemphigus vulgaris Proteins in intercellular junctions of epidermal celts (epidermal cadherin) Antibody-mediated activation of proteases, disruption of intercellular adhesions Skin vesicles (bullae) Vasculitis caused by ANCA Neutrophl granule proteins, presumably released from activated neutrophils Neutrophil degranulation and inflammation Vasculitis Goodpasture's syndrome Noncollagenous protein in basement membranes of kidney glomerul and lung alveoli Complement- and Fc receptor-mediated inflammation Nephritis, lung hemorrhage Acute rheumatic fever Streptococcal eel wal antigen: antibody cross-reacts with myocardial antigen Inflammation, macrophage activation Myocarditis, arthritis Myasthenia gravis Acetylcholine receptor Antibody inhibits acetylcholine binding, down-modulates receptors Muscle weakness, paralysis Graves' disease (hyperthyroidism) TSH receptor Antibody-mediated stimulation of TSH receptors Hyperthyroidism Insulin-resistant diabetes Insulin receptor Antibody inhibits binding of insulin Hyperglycemia, ketoacidosis Pernicious anemia Intrinsic factor of gastric parietal cells Neutralization of intrinsic factor, decreased absorption of vitamin B,2 Abnormal erythropoiesis. AN podle typu převažující hypersensitivní reakce - typ II, III a IV Autoimmune disease Autoantigen Consequence Antibody against cell-surface or matrix antigens (type II) Autoimmune hemolytic anemia Rh blood group antigens, 1 antigen Destruction of red blood cells by complement and phagocytes anemia Autoimmune thrombocytopenia purpura Platelet integrin gpllb:llla Abnormal bleeding Goodpasture's syndrome Non-collagenous domain of basement membrane collagen type IV Glomerulonephritis, pulmonary hemorrhage Pemphigus vulgaris Epidermal cadherin Blistering of skin Acute rheumatic fever Streptococcal cell wall antigens. Antibodies cross-react with cardiac muscle Arthritis, myocarditis, late scarring of heart valves Graves' disease Thyroid-stimulating hormone receptor Hyperthyroidism Myasthenia gravis Acetylcholine receptor Progressive weakness Insulin-resistant diabetes Insulin receptor (antagonist) Hyperglycemia, ketoacidosis Hypoglycemia Insulin receptor (agonist) Hypoglycemia Figure 11-1 part 1 of 3 The Immune System, 2/e {€> Garland Science 2005) Autoimmune disease Autoantigen Consequence Immune-complex disease (type III) Subacute bacterial endocarditis Bacterial antigen Glomerulonephritis Mixed essential cryoglobulinemia Rheumatoid factor IgG complexes (with or without hepatitis C antigens) Systemic vasculitis Systemic lupus erythematosus DNA, histones, ribosomes, snRNP, scRNP Glomerulonephritis, vasculitis, arthritis Figure 11 1 part 2 of 3 The Immune System, 2/e (0 Garland Science 2005) Autoimmune disease Autoantigen Consequence T cell-mediated disease (type IV) Insulin-dependent diabetes mellitus Pancreatic p'-cell antigen (j-cell destruction Rheumatoid arthritis Unknown synovial joint antigen Joint inflammation and destruction Multiple sclerosis Myelin basic protein, proteolipid protein Brain degeneration. Paralysis Celiac disease Gluten modified by tissue transglutaminase Malabsorption of nutrients Atrophy of intestinal villi Figure 11-1 part 3 of 3 The Immune System, 2/e (© Garland Science 2005) Prevalence a pohlavně specifické rozdíly Goes' disease Rheumatoid arthritis Hashimoto's thyroiditis Vitiligo Typo' diabetes Pamldous anemia Multiple sclerosis Gomenjlonephritis Systemic Lupus E Sjogren syndrome CO Rate HX 800 pefüOrjoo Sex-based differences in AD can be traced to sex hormones — sex hormones circulate throughout the body and alter immune response by influencing gene expression — (in general) estrogen can trigger autoimmunity and testosterone can protect against it Gender-difference in immune response — 9 produce a higher titer of antibodies and mount more vigorous immune responses than cf — 9 have a slightly higher Cortisol secretion than cf — 9 have higher levels or CD4+T-cells and serum IgM Pregnancy — during this, 9 mount more of a TH2-like response — the change in hormones creates an antiinflammatory environment (high Cortisol levels) — diseases enhanced by TH2-like responses are exaggerated — diseases that involve TH1 inflammatory responses are suppressed Fetal cells can persist in the mother's blood or the mother's cells may appear in the fetus (microchimerism) — this can result in autoimmunity if the fetal cells mount an immune response in the mother's body (or vice versa) príklady některých systémových an (sle a revmatoidní artritída) Systémový lupus erythematoides (SLE) Revmatoidní artritída (RA) affected organs — skin (butterfly rash) — vessels (vasculitis) — kidneys (lupus nephritis) — joints (arthritis) — CNS (encephalopathy) Immune mechanism — abnormal activation of DNA specific B cells by engagement of their TLR9 (binding of CpG motifs) and DNA receptors by antigens released from apoptotic cells — production of Ab against nuclear components • dsDNA (double stranded) • RNA-protein complexes • histones — complexes are formed (e.g. anti-dsDNS-DNA) and deposited in predilection sites (e.g. glomerulus, synovia, vessel wall) or in sites of death cells releasing DNA and DAMPs • this explains rash after sun exposure (UV-induced apoptosis of keratinocytes) very variable clinical course — 80% patients survive 10 yrs after diagnosis Molecular mechanism operating in RA T cells (primarily CD4+ memory cells) invading the synovial membrane produce IL-2 and IFN-gamma. Through cell-cell contact and through cytokines (produced also by APCs, such as IFN-gamma, TNFa IL-17) these T cells activate monocytes, macrophages and synovial fibroblasts. They then overproduce proinflammatory cytokines, mainly TNF-, IL-1 and IL-6 causing chronic inflammation. These cytokines also activate a variety of genes characteristic of inflammatory responses, including genes coding for various cytokines and matrix metalloproteinases (MMPs) involved in tissue degradation. TNF- and IL-1 also induce RANK expression on macrophages which, when interfering with RANKL on stromal cells or T cells, differentiate into osteoclasts that resorb and destroy bone, in addition, chondrocytes also become activated, leading to the release of MMPs Demographics — affects 1-2% of worldwide population — patients are 75% women between 40-60 years of age RA mostly damages joints, but it can also affect the heart, kidneys and eyes Molecular mechanism — T-cell mediated AD, however Ab are Also produced • Rheumatoid Factor (Rf): IgM antibodies to Fc fragment of IgG — HLA-DR4 association (MHC II) Mechanism of Tissue Damage — Invasion of T lymphocytes in the synovia and pro-inflammatory cytokine production — immune cells accumulate in the joints (bones, cartilage, surrounding tissue) and cause chronic inflammation. The inflammation causes destruction and scarring of the joints. Later the joints deform and lose their structure Inflammatory response of the synovial membrane ('synovitis') Transendothelial influx and/or local activation of a variety of mononuclear cells, such as T cells, B cells, plasma cells, dendritic cells, macrophages, mast cells, as well as by new vessel formation. The lymphoid infiltrate can be diffuse or, commonly, form lymphoid-follicle-like structures. The lining layer becomes hyperplastic (it can have a thickness of >20 cells) and the synovial membrane expands and forms villi. However, in addition, the hallmark of RA is bone destruction . The destructive portion of the synovial membrane is termed 'pannus', and the destructive cellular element is the osteoclast; destruction mostly starts at the cartilage-bone-synovial membrane junction. Polymorphonuclear leukocytes are found in high numbers in the joint fluid, enzymes, together with enzymes secreted by synoviocytes and chondrocytes, lead to cartilage degradation. Nature Povtowa I oruo. Discovery Nature Review* | Drug Discovery príklady an v git (celiakie a nespecifické střevní záněty) GIT je lokalizací mnoha běžných AN autoimmune • — salivary glands • Sjögren syndrome — stomach • atrophic gastritis — intestine • celiac disease • inflammatory bowel disease — Crohn's disease — ulcerative colitis — liver • primary sclerosing cholangitis • primary biliary cirrhosis • autoimmune hepatitis — pancreas • autoimmune pancreatitis lergy - food allergy (e.g. milk or dairy products) • more precisely particular proteins • difference from lactose intolerance due to enzyme disorder (lactase deficiency) — extremely frequent - mainly due to the fact that lifetime ability to digest milk (i.e. lactose) is considered a normal state — however, most mammals and part of human population loses the activity of lactase after weaning — the lifetime activity could be considered exceptional -persistence of lactase » genetic polymorphism (geographical distribution is evidently a consequence of genetic selection) in promoter of gene for lactase • highest prevalence of lactase persistence in Europe in Swedes a Danes (-90 %) • Czech population ~ 70 % • lowest in Turks (~ 20 %) • outside Europe high fervency of persistence e.g. in desert nomadic populations in North Africa • the reason for selection of persistence haplotype in northwest Europe could be the richer source of calcium in low vit. D generation climate — manifestation » intestinal discomfort after fresh milk intake (not after diary fermented products such as cheese or yogurt) » diarrhea, flatulence, abdominal pain Atrofická gastritída destruction of mainly parietal cells by cytotoxic lymphocytes • compensatory t gastrin antibodies against • intrinsic factor (IF) and complexes IF/B12 • Na/K-ATPase • carbonic anhydrase • gastrin receptor consequences - achlorhydria leading to sideropenic anaemia - later megaloblastic (pernicious) anaemia - precancerosis ■ normally DYSPLASIA CARCINOID SMALL INTESTINE LARGE INTESTINE Muscularis Mucosae the Submucosa Tunica Muscularis Externa Celiakie Patofyziologie celiakie HLA = Human Leukocyte antigen. synonyms: celiac sprue, gluten-sensitive enteropathy, gluten intolerance T-cell mediated autoimmune reaction against intestinal mucosa (mainly duodenum and jejunum) initiated by gluten and its products (gliadins) prevalence -1% of populations — but commonly underdiagnosed manifestation: — often starts in child after the stop of breast feeding when flour is introduced (though latency of many years) — but anytime in life symptoms are very variable!!! — typical — untypical etiology - gen. predisposition- • variants of MHC II genes - DQ2 and DQ8 haplotypes - celiac d. often associated with other autoimmunities, e.g. T1DM • other non-HLA alleles - external factors • gluten in diet - gluten consist of two component (= peptides) gliadin andglutenin polypeptides » i.e. a heterogeneous mixture of gliadins (prolamines) and glutenins - relatively resisitant to digestion by GIT enzymes, and allow immunogenic peptides to reach mucosal surfaces _.• • infection by adenoviruses molecular mimicry ^ damage of intestinal barrier Co je gluten? gluten (= proteins) is a part of endosperm of cereals (especially wheat) — "gluten" is a term applied specifically to the combination of the prolamin proteins (called gliadins) and the glutelin proteins (called glutenins) that are found in wheat gluten is found in the following grains: — wheat, barley, bulgur, rye, spelt, oats (possibly, the proportion of individuals with gluten sensitivity that are also sensitive to the storage proteins in oats is likely less than 1%), kamut, triticale, semolina, pumpernickel, farro gluten is not found in the following grains: — rice (all varieties), buckwheat, teff, amaranth, quinoa, corn, hominy, millet gluten adds elasticity to dough (makes bakery products chewy, pizza dough stretchy, and pasta noodles elastic so that they can be pulled through the pasta press without breaking when they are made — thus, getting a desirable texture in gluten free baked goods can be difficult Bran: Outer Sheir ~ Provides liber. GLUTEN (GLIADIN + GLUTENIN) Patoyziologie celiakie pathogenesis HLA-DQ2 and HLA-DQ8 prefer to bind peptides with negative charges, but gluten peptides are usually devoid of these — enzyme transglutaminase 2 (TG2) can modify gluten peptides, either by introducing negative charges through deamination or through crosslinking gliadin peptides with each other or the TG2 enzyme itself — TG2 is usually expressed intracellularly in an inactive form and is released when inflammation or other stressors damage the cell • thus under normal circumstances gluten proteins are unaltered and cannot bind to HLA-DQ • if TG2 is present and native gluten peptides are presented to CD4+ cells, IFNy is released and an inflammatory response occurs • this in turn leads to more damage and release of TG2, and this loop leads to the damage caused by celiac disease — HLA-DQ8 usually binds to peptides that are not proline rich, and thus several deamination steps are required before the gluten peptide becomes immunogenic • this limits the risk of developing celiac disease in individuals that are only HLA-DQ8+ activated gluten-specific CD4+ T helper 1 (Thl) cells secrete high levels of proinflammatory cytokines (e.g. IFN)gamma and IL-21 that promote the activation of intraepithelial cytotoxic CD8+T lymphocytes Th2 response - via B cells - leads to production of antibodies against gliadin, reticulin and transglutaminase Brush border-TG2 MECHANICAL STRESS o o o O Dietary gluten O peptides Gut lumen INFECTIONS)^^ Bacterial toxins Damage to fibroblast and endothelial cells I» cf ^ o UP /I ^^^Lr/^ Gluten deamination ^^^^ ^^^^i/^ gncj cross_|jnkjng & by tTGase Mucosal epithelium TG2 mina propria Release of tTGase and activation í Release of tight junction proteins Presentation to dendritic cells Further contribution to autoimmunity 1 Mucosal destructions and epithelial cell apoptosis © HLA Late exposure to bacterial antigens (IL-12) ® t Production of proinflammatory cytokines (q) (TNF-a, IFN-y)w lunity \ Production of IgG, IgM, IgA antibodies to gluten, transglutaminase, tight junction proteins and other tissue proteins. ' Antigei "presentation and T cell receptor stimulation Depiction of the intestinal mucosa with emphasis on the factors involved in the development of celiac disease in individuals with HLA-DQ2/DQ8 positive Manifestace celiakie — consequences of auto-aggressive inflammation - villous atrophy, crypt hyperplasia and intraepithelial lymphocytosis (typical markers for celiac disease) clinical course & symptoms — diarrhea — abdominal pain — bloating — malabsorption of main nutrients, vitamins, trace elements • hypo-/malnutrition or weight loss — non-gastrointestinal manifestation • children: short stature, anemia, neurological symptoms • adults: dermatitis herpetiformis, anaemia, reduced bone density, infertility, irritable bowel syndrome, dyspepsia, esophageal reflux, neurological symptoms — in 20-40 years risk of intest, lymphoma (50%) or carcinoma (10%) Upper Jejunal Mucosal Immunopathology If ft Ifl kj? , ...1 Other 5% Diarrhea 43% Abdominal Pain 5% Weight Loss 6% Bone disease 6% Anemia6% Incidental 10% Screening 17% Inflammatory bowel diseases (IBD) "Maybe she's gluten intolerant." both Crohn's disease (CD) and ulcerative colitis (UV) exhibit certain similar features — manifestation in young adults — clinical course • intermittent flares (exacerbations) followed by remissions — genetic predisposition • though different genes in CD and UC — abnormal reactivity of innate immune system to intestinal microbiota (bacteria) — abnormal lymphocyte activity and subsequent cytokine spectrum • predominance of Thl/Thl7 in CD • atypical Th2 in UC localization — m. Crohn - any segment of GIT, transmural, granulomatous inflammation — ulcerative colitis - only rectum and Healthy colon colon, inflammation confined to mucosa Ulcerative Colon Imunitní systém střeva Etiologie nespecifických střevních zánětů Mucus layer I Mesenteric lymph node Extracellular matrix NMurt Rtvicwt I Immunology Unique with respect to its close apposition to intraluminal bacteria, which are separated from the underlying lamina propria by only a single layer of epithelial cells The epithelial-cell layer is comprised of absorptive and secretory cells, goblet cells (formation of the protective mucus layer) and Paneth cells. Immune Microfold cells (M cells) and dendritic cells (DCs) sample intestinal luminal contents - under normal conditions, the innate immune cells in the intestinal mucosa are largely tolerogenic, in order to prevent inflammatory responses to beneficial commensal bacteria in the gut - macrophages and dendritic cells have a key role in this regard. Intestinal macrophages are involved in phagocytosis of pathogens and removal of cell debris. Unlike most macrophages, intestinal macrophages do not produce proinflammatory cytokines in response to phagocytic activities due to downregulation in the expression of certain cell surface receptors, like CD14 (which reduces ability to response to lipopolysaccharide) and several of the TLRs - CD103+ DCs in the gut are able to induce the formation of regulatory T cells, which are one of the cell types involved in the adaptive component of tolerance - the anti-inflammatory environment of the intestinal mucosa is promoted by the presence of cytokines such as IL-10 and TGFb which are associated with many anti-inflammatory functions The presence of either pathogenic bacteria or disruption of the epithelial-cell barrier results in activation and migration of DCs to the mesenteric lymph nodes, where they activate naive T cells, which then undergo differentiation under the influence of factors released by DCs and other stromal elements. genetic factors cases abnormal immune reactivity of innate immune system — CD • mutation causing altered expression of pattern-recognition receptors (PRRs), e.g. Toll-like receptors (UC) or NOD2 and abnormal activity of autophagy -> bacterial invasion and defective bacterial clearance -> low production of pro-inflammatory cytokines -> granulomatous lesions — UC • primary defects in intestinal barrier (tight junctions) -> excessive production of pro-inflammatory cytokines (TNFa) -> inflammatory infiltration of mucosa by leucocytes — abnormal adaptive immune response is likely secondary • therefore some propose CD and UC are in fact immune deficiencies environmental factors — incidence rises in Europe and N. America — the same is now evident on southern hemisphere and in Asia microbial factors — gut microflora is very complex • Bacteroidestes • Firmicutes • Actionobacteria • Preoteobacteria — modified by plethora of factors • way delivery (vaginal vs. CS), use of ATB (esp. in sensitive periods such as infancy), quality and quantity of food, food additives, xenobiotics, drugs etc. Tolerance controlled inflammation Chronic inflammation Crohnova choroba = ileitis terminalis, enteritis regionalis chronic, relapsing, systemic inflammatory disease of — commonly small intestine • but can affect any part of GIT beginning with oral cavity to anus • manifestation typically between 3. to 6. decade, more often women — extraintestinal manifestations • arthritis • uveitis • pyoderma gangrenosum and erythema nodosum manifestation & clinical course — periods of exacerbations (stomach pain, diarrhea, fever, seizures, blood in stools (enterororhagia)/remissions histopathology — granulomatous type of inflammation affects all layers of intest. wall — ulcerations and bleeding — penetrated ulcers create fistulas (often perirectal) — affected areas interspersed by unaffected Crohn's colitis ulcers Appendix * Crohn's iletis -—Small intestine A Etiopatogeneze CD multifactorial — genetic factors (= predisposition) lead to abnormal immune response of intest. mucosa to natural commensal bacterial antigens (>500 bact. strains, aerobes and anaerobes) • normally opposed by production of defensins • GWAS — mutation in gene for CARD15 — autophagy protein ATG16L1 — many other loci — triggering environmental factors nor known (infection?) = sterile animals protected • lipopolysaccharide, peptidoglycan, flagellin,... • suspects Mycobacteria, Listeria and Yersinia (the latter two unconfirmed) INTESTINAL MICROFLORA 1014micro-organisms, >500 ditferentes species Stomach 102tOl03 Lactobacilli Streptococci Lactobacilli Enterc-bacteria r Enterococcus FaecaNs I Bacteroides Bifidobacteria Peptococcus Pept o st reptococc Ruminococcus Clostridia Lactobacilli and. Duodenum Jejunum founi Colon with appendix <10"b 103to 107 109to10'2 Homeostasis of m & * | Bacterid _*© * Cyto invasion microbial rtktea T ) \ < O Chemo kine □hi nishsci release of a limici 3bial peptides * * »MDP NOD2 L1007fsirisC c Ml /\r~r~ infraepthelia! \ -} bacterial ^ ' V_^y load reaction to intraluminal bacteria - normally "controlled inflammation" intracellular recognition of components of bacterial wall (pathogen-associated molecular patterns, PAMPs), e.g. muramyl-dipeptide (MDP) by NOD2 (product of CARD15 gene) lead to oligomerization and activation of NFk-B • secretion of chemokines and defensins by Paneth cells variants of NOD2 associated with Crohn's d. lead to deficient epithelial response, loss of barrier function and increased exposition to intest. microflora • impaired secretion of chemokines and defensins • altered expression of pattern-recognition receptors (PRRs), e.g. Toll-like receptors • production of inflammatory cytokines • activation of dendritic cells and production of Ig and activation of Thl lymph. Defective bacterial clearance in CD Defective post-translational modifications in macrophages direct cytokines and chemokines to the lysosome, thus reducing secretion and leading to decreased neutrophil recruitment and persistence of bacteria in the intestinal mucosa. Vesicle transport defects also lead to reduced bacterial clearance in the autophagolysosome. Impaired epithelial barrier integrity contributes to increased bacterial load, thereby exacerbating the adaptive immune response. Mutations in the NOD2 receptor reduce the acute inflammatory response to bacteria and amplify the chronic inflammatory response by inhibiting the transcription of IL-10 Ulcerativni kolitida Imunologie v kostce two peak incidence between 20 - 40. na after 50 years of age typically Caucasian race, north-south gradient inflammation limited to mucosa — starts at the bottom of Lieberkuhn's crypts (infiltration by immune cells) • mainly rectum and sigmoideum — hyperemia, abscesses and ulcerations, bleeding, pseudopolyps, event, strictures — high activity of TNFa (—> treatment with anti-TNFa antibodies) clinical course — periodical = exacerbations x remissions (diarrhea, bleeding, abdominal pain, fever) — extraintestinal manifestations (5 - 15%): • polyarthritis, osteoporosis, uveitis, cholangitis — chronic anemia, strictures, hemorrhoids — carcinoma in severe form indication for colectomy Macrophage shows antigen to other 2 he antljte s activate the Helper Tee Is. 3 Helper t cells start dividing to make more helper t cells. Helper T cells activate the killer t cells so thai they can kill off the infected cells. Hel pei T c o they ca lis then activate theBce make a lot of antibodies Is Antibodies attach onto bacteria. 5 6 P rot sens attach themselves to then they destroy the pathogens. pro, Artdl st the macrophages eat up pathogens * *a» 8 Ol*