Non-Specific Immunity
Innate (natural, native, non-specific)
immunity
• Always present, ready to recognise and eliminate
microbes. May be stimulated also by nonmicrobial
agents.
• Frequently eliminates microbes before the specific
immunity becomes active.
• Receptors are encoded in the germline, are not
a product of recombination of genes.
Differences between the Innate and
Acquired Immunity
• Innate Immunity
– Universal
– Rapid
– Lacks memory
• Acquired Immunity
– Not universal
– ‘Slow’ to develop
– Memory
– Specific but in some situations
reacts to autoantigens
– ‘Plays to the tune of the innate
immune system’
“Trained immunity“
•
It has recently been shown that some mechanisms of non-specific immunity
have the ability to respond more intensively, effectively, after repeated
stimulation by some (non-specific) stimuli.
It can be detected in NK cells, dendritic cells, myeloid cells as well as some
stem cells.
Epigenetic mechanisms are involved
In addition to the body's defense, participation in the pathogenesis of several
diseases accompanied by chronic inflammation is also being considered.
Signals of danger
- EXOGENEOUS (PAMPs)
-ENDOGENEOU (e.g. STRESS PROTEINS
RELEASD FROM NECROTIC CELL)
Inborn immunity – activating signals
(alarmins)
Pathogen-Associated Molecular Patterns (PAMPs)
(C. A. Jeneway,Jr, 1989)
microbial structures, motifs, present in large groups
of microorganisms, necessary for their life
e.g. lipopolysachrides, lipopeptides, peptidoglycans, manose
nonmetylated CpG present in bacterial DNA,
dsRNA of RNA-vises
Danger, Damage-Associated Molecular atterns (DAMPs)
(Polly Celine Eveline Matzinger,1994)
Molecular structures of the host macroorganism
e.g. HSP60, HSP70, fragments of fibrinogen, fibronectin,
hyaluronan..
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Differences between innate and specific immunity
PAMPs – pathogen-associated molecular patterns exogenou
substances activating non-specific immunity (Endotoxin, mannose,
double-stranded RNA, unmelylated CpG nucleotides)
DAMPs – danger associated molecular patterns – endogenous
substances stimulating non specific immunity – heat shock proteins, uric
acid
PRR- Pattern recognition receptors - recognize PAMPs, DAMPs.
TOLL-like receptors –surface or intracellular receptors recognizing
various PAMPs. Expressed on dendritic cells, macrophages,
granulocytes, epitelial cells…. They induce activation of these cells.
TOLL-LIKE RECEPTORS
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Activation by Toll-like Receptors and by Cytokine Receptors
Basic components of non-specific
defence
• Non Specific barriers
– Anatomical/Physiological
• Acute phase reactants and Inflammation
– Complement/Interferons/CRP
• Innate cells
– PMN/Macrophages/NK cells
Non-specific barriers of human body
The Complement System
General features of the Complement
System Activation
• Inactive, preformed protein is activated by the
proteolytic cleavage.
• It is cleft into the smaller part (called a) and a bigger
part (called b).
• Usually the bigger part has also proteolytic activity,
while the smaller part has various other biological
activities (chemotactic, anaphylatoxic).
• Component C6-C9 are activated without cleavage,
they just „attach“ to the complex of the other
complement components.
anaphylatoxin
inflammation,
phagocyte recruitment
C4a, C3a, C5a
lytic pathway
formation of membrane-attack
comlex, lysis of pathogens
C5b, C6, C7, C8, C9
opsonization
phagocytosis
C3b
Alternative pathway
spontaneous activation
C3 C3b
Bf Factor D Bb
Lectin pathway
mannose binding
MBL
MASP-1
MASP-2
C4/C2 C4b/C2b
Classical pathway
antibody binding
C1q/r2/s2
C4/C2 C4b/C2b
C3 convertase
C3 C3a + C3b
C3b/Bb C4b/C2b C4b/C2b
C5 convertase
C5 C5b
Complement system
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The Complement System
Complement system activation
• Classical pathway:
– Complexes IgG-antigen, IgM-antigen,
– C-reactive protein
• Alternative pathwas
– Lipopolysaccharide of G- bacteria
– Cell wall of some bacteria
– Cell wall of the yeasts (zymozan)
– Aggregated IgA
• Lectin pathway:
– Mannose and other sacharides
Complement system activation
membranolytic omplex
Classical
pathway
C1
C4
C2
Lectin pathway
cesta
MBL
MASP 1, 2
C4
C2
Alternative pathway
C3b
B
D
P
C3 convertase
C3 C3b
C5 C5b
C5b
C6
C7
C8
C9
C1
C2
C4
C2aC4b
C3
C3a
C3b
C5
C5a
C5b
C5b, C6,
C7, C8
IgG
C9
Classical pathway complement activation
Effect of C9
Actiation of Alternative Pathway
of the Complement system
C3
C3 C3aC3a B Ba
Activating
surfaces + proteolysis
D, P
C3b
C3 Convertase C5 Convertase
C3b, Bb, C3bC3b, Bb
Alternative pathway of the
complement system
• Initiated by spontaneous activation of C3 on the
surface of some bacteria (eg due to LPS) or
yeast (eg due to zymosan),
• Comonent B is activated
• Component D and P (properdin) participate in
the stabilization of the complex.
• Alternative C3 convertase (C3bBb) is formed.
Lectin (third) pathway ot the
complement system activation.
• Mannose-binding lectin (MBL) binds to several cell surface
polysaccharides.
• Activated MBL activates C2 and C4.
• MBL is a polymer composed of three subunits.
• Several exon and promoter polymorphisms lead to a very
low level ("deficit") of MBL (5-10% of the population).
• Most people with MBL deficiency have no immunodeficiency
symptoms.
Activation of classic and lectin complement pathways
Biological effects of activated
complement system
• C9 - cytolytic effect
• C3b - opsonisation
• C3a, C5a – anaphylatoxins, liberation of
histamine
• C5a - chemotaxin
Regulation of the Complement System
• Factors present in plasma
– Classical pathway – mainly C1-inhibitor - C1-INH
(deficiency leads to hereditary angioedema).
– Alternative pathway – factor H, factor I
• Faktors on cell membranes:
– CD59, CD55 (DAF - decay accelerating factor) - CD46
Patothogenetic Significance of the
Complement System
• Deficit of components of the classical and alternative
pathways – proneness to bacterial infections and to systemic
autoimmune diseases.
• C1-INH deficiency: hereditary angioedema.
• Mutations of factor H – atypical hemolytic-uremic syndrome.
• Several polymorphisms of factor H are linked to senile
macullar degeneration.
• Paroxysmal night hemoglobinuria – caused by mutations of the
gene PIG-A (product if this gene binds CD 55 and CD 59 into
cytoplasmatic membrane).
Phagocytosis
Phagocytic cells
• Polymorphonuclear granulocytes
• Monocytes + macrophages
• Dendritic cells mainly non-activated
cells. After activation they loose most of
their phagocytic activity.
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Polymorphonuclear granulocyte
Normal blood count (in adults)
• Erythrocytes: 4-5 x 1012/l
• Thrombocytes: 150-300 x 109/l
• Leukocytes: 4-9 x 109/l
– Granulocytes: 55-70%
– Eosinophils: 1-4%
– Basophils: 0-1%
– Lymphocytes: 24-40%
– Monocytes: 3-8%
Macrophages
• Derived from blood monocytes.
• Connective tissue macrophages
– Kupffer cells (liver)
– Alveolar macrophages (lungs)
– Microglia (CNS)
– Osteoclasts (bone)
– Peritoneal macrophages
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Development of macrophages
Two phases of interaction between
phagocytic and endolethelial cells
• Rolling - reversible interaction due to binding
between endothelial selectins and their ligands
on the surface of leukocytes (eg sialyl-LewisX).
• Stable binding - formed after activation by proinflammatory
stimuli. It is given by the interaction
between leukocyte integrins and their ligands on
endothelium - eg ICAM-1.
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Extravasation of leukocytes
Natalizumab
• A humanized monoclonal antibody that binds to
the α4 integrin (which binds to the integrin
receptor VCAM-1).
• Adhesion and subsequent transfer of leukocytes
(mainly T-lymphocytes) to the extravascular
spaces is blocked.
• Used in the treatment of multiple sclerosis, and
recently also in Crohn's disease.
“Classical“ phases of phagocytososis
• Chemotaxis - targeted movement of cells
against the concentration gradient of
chemotactic factors (chemotaxins).
• Adhesion
• Ingestion – formation of a phagosome, which
consequently fuses with a lysosome to form a
phagolysosome.
• Killing and Intracellular degradation of microbes
Chemotaxins
• Attract phagocytic cells
• Products of destroyed cells
• C5a
• IL-7, IL-1
• Leukotriens
Opsonins
• Substances enhancing phagocytic process by
improving adhesion of the particle to the
phagocytic cell.
• Specific: IgG, (IgM only indirectly by activation of
the complement system)
• Non- specific: C3b, fibronectin….
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Steps of phagocytosis
Killing mechanisms of phagocytic
cells
• Reactive metabolites of oxygen (H2O2, hydroxyl radical
(.OH), superoxide aniont (O2
-), singletted oxygen (.O2)
• Reactive nitrogem intermediates (NO, NO2)
• Hydrolases: protease, lipases, DNAses
• Low pH
• Lysozyme
• Lactoferin
• Defensins – antimicrobial polypeptides
Lysozyme
• Cleaves cell walls of G+ bacteria
• Present in granules of neutrophil
granulocytes, in plasma, secretions.
Defensins
• Polypeptides with antibiotic-like effect on bacteria
and fungi.
• Produced mainly by granulocytes and by
epithelial cells.
• Lead to desintegration of cell membranes,
formation of pores in membranes .
• Main groups are a and b defensins
Natural killers (NK cells)
• Originate in non-T non-B lymphocyte lineage.
• Morphologically: large granulated lymphocytes (LGL).
• Recognition of target cells in antigen non-specific.
• Virus infected and tumor cells are the main tragets.
• Target cells are recognised mainly by decreased HLA-I
expression.
• Cytotoxic mechanisms are similar to Tc cells: perforin and
induction of apoptosis.
• Target cells can be recogised by the Antibody Dependent
Cellular Cytotoxicity (ADCC).
• Produce various cytokines, e.g. IFN-g, IL-12.
Large granulated lymphocyte
Antibody dependent cellular cytotoxicity (ADCC)
Fc receptor
Virus-infected Cell
NK Cell
perforin granzyne
IgG
Fab
Fc
Epitope
Interferons (IFN)
• Type 1: IFN a, IFN b – produced mainly by
virus-infected cells (fibroblasts, granulocytes.
Lead to inhibition of the virus replication in target
cells.
• Type 2 - „Immune interferon“: IFN g: is produced
by activated TH1+ cells, NK cells . Induces
activation of macrophages.
• Interferon type 3 - IFN l (and other molecules) similar
to IFN-I
Antiviral effect of interferons
• Bindies to a specific receptor (heterodimer) of
infected and still uninfected cells.
• Activation of a number of anti-virus
mechanisms:
– IF-2 protein kinase - phosphorylates (thereby
inactivates) the initiation factor IF-2 - necessary for
proteosynthesis.
– 2´5´oligoadenylate synthetase - activation of
ribonucleases cleaving viral RNA.
The action of interferon (IFN)
Virus
Viral nucleic
acid New viruses
Antiviral proteins block
viral reproduction
Interferon molecules
produced
Interferon binding simulates
cell to turn on genes for
antiviral proteins
Host cell 1
• Infected by virus
• Makes interferon
• Is kiled by virus
Host cell 2
• Entered by interferon from cell 1;
• Interferon induces changes that protect it
Inflammation
• A genetically fixed, rapid response to a tissue damage.
• Acute inflammation plays a crucial role in the protection of the body,
however chronic inflammation may lead to an organism damage.
• Components of the innate immunity play a crucial role.
• Local consequences of inflammation
– Increased blood flow to affected area
– Recruitment of phagocytes to affected area, particularly
neutrophils and macrophages
– Alteration of vascular permeability leading to entry of soluble
molecules from the plasma
Inflammasome
It is a protein oligomer consisting of intracytoplasmic signaling
molecules (caspases and others).
It is expressed in myeloid cells It is considered part of innate
immunity.
The specific composition of the inflammasome is dependent
on the activators that cause its assembly.
The inflammasome supports the maturation of proinflammatory
cytokines.
Local mediators of inflammation
• Products of activation of the kinin, complement, and coagulation
systems. Usually C3a and C5a plays a significant role.
• Vasoactive amines – histamin, serotonin - reased from the
damaged cells or stimulated macrophages.
• Metabolites of arachidonic acid
• Platelet activating factor
• Produkty of monocytes and granulocytes: IL-1, TNF-a, IL-6, IL-
18, chemokines, NO,
• Produkts of activated lymphocytes: TNF-a, IL-6, IFN-g,
chemokines
General symptoms and signs of
inflammation
• Orchestrated mainly by IL-1, IL-6, TNF-a
• Fever (effect of cytokines on hypothalamic
centers)
• Fatigue, somnolence
• Loss of appetite
• Laboratory signs: leukocytosis, increased ESR,
increase in accute phase proteins, decreased
levels of iron and zinc in serum.
Accute-phase proteins
• Serum levels are increased during inflammation
• Produced by the liver after stimulation by IL-1,
IL-6, TNF-a
• Best known: C-reactive protein
• Others: Complement components, A1-AT,
fibronectin..
Accute phase response
Initiation of inflammatory response
Skin Bacteria
1. 2. 3.
Skin
Pin
Blood clot
Red blood cells
Phagocyte
Step 1
Damaged tissues increasing blood
flow to the area
Step 2
Histamines cause capillaries to
leak, releasing phagocytes and
clotting factors into the wound
Step 3
Phagocytes engulf bacteria,
dead cells, and cellular debris
C3a
C5a
Drugs modulating inflammatory process
• Non-steroidal anti-rheumatic (anti-phlogistic)
drugs (acidosalicylic acid, paracetamole,…)
• Antimalarics
• Glucocorticoids
• Monoclonal antibodies against inflammatory
cytokines and adhesion molecules
• Janus kinase inhibitors