Immunology-introduction



Immune system
•One of the basic homeostatic mechanisms of the body.
•Its function is the recognition of foreign/dangerous substances.
•The dangerous substances trigger complex reactions which result in elimination of those
substances.
•

 Immune system
•Recognizes foreign/dangerous substances from the environment (mainly microbes)
•Is involved in elimination of old and damaged cells of the body.
•Attacks tumor and  virus-infected cells.

Functions of the immune system
•Deffence
•
•Autotolerance
•
•Immune surveillance

Antigen
•Substance, that is recognised by the immune system as a foreign and triggers immune reaction
(immunogenicity).
•
•Products of the immune reaction (antibodies, T-lymphocytes) react with the antigen.

Requirements of immunogenicity
•Foreign (unknown) for the immune system
•
•High molecular weight (> 6 kDa)
•
•Chemical complexity

Antigen – basic components
•Carrier part of the molecule
•
•Antigenic determinant- epitope  (cca 5-7 aminoacids)

Antigen and epitope
17-03_Epitopes_1


Chemical composition of antigents
•Proteins – usually very good antigens.
•Polysacharides- usually only as a part of glycoproteins.
•Nucleic acids- poor antigenicity, limited to complexes with proteins
•Lipids – only exceptionally, best known are sfingolipids.

Hapten
•Low-molecular weight substances that trigger immune reaction after binding to various proteins of
the body.
•They react with products of the immune reaction.
•Typical examples are metals (Cr, Ni)  that trigger type IV immunopathological reactions. Drugs
(antibiotics, local anestetics) cause type I immunopathological reaction.

Immunogenicity of hapten
17-04_Haptens_1


Cross reactivity of antigens
•Products of the immune reaction may, in some conditions, react with substances that are very
different from the initial immunogen.
•Immunological cross-reactivity not necessary mean similar chemical composition.
•The degree of cross reactivity may be different.
•Cross reactivity is important in pathogenesis of several autoimmune diseases.
•

Cross reactivity of antigens
antibody
Benjamini E, Leskowitz S. 1988

Adjuvants
•Substances, that when mixed with antigen, non-specifically  enhance immune reaction against the
antigen.
•Freud´s adjuvant: killed Mycobacterium tuberculosis + water-in-oil emulsion. Used in veterinary
medicine.
•Alum precipitate - AL(OH)3 - used in human medicine

Two branches of the immune response
•Innate, nonspecific – very quickly recognizes most foreign substances and eliminates them. There
is no memory.
•Adaptive, specific – high degree of specificity in distinction between self and non-self.  The
reaction requires several days to be effectively triggered. There is immune memory.

Cells of the immune system
•Main cells of the immune system
–Lymfocytes (T a B)
•Accessory cells of the immune system
–Granulocytes
–Monocytes
–Tissue macrophages
–Mast cells
–Dendritic cells
–NK cells
–Endotelial cells
–Thrombocytes, erythrocytes, fibroblasts, epitelial cells
–

anatomie9
Majority of immune system cell originate in bone marrow
Roitt/Broskoff/Male: IMMUNOLOGy, 4th ed

Lymphocyte – central cell of the immune system



Auxiliary cells of the immune system






Antigen- presenting cells



anatomie1
Organs of the immune system
Roitt/Broskoff/Male: IMMUNOLOGy, 4th ed

anatomie3
Lymph node
Roitt/Broskoff/Male: IMMUNOLOGy, 4th ed

Snímek 003
The Spleen


anatomie2
Histology of the Spleen
Roitt/Broskoff/Male: IMMUNOLOGy, 4th ed

Snímek 006
Payer ´s Patches


Snímek 007
Circulation of lymphocytes in the body


anatomie4
Circulation of Lymphocytes in the body
The role of High Endotelial Venules
Roitt/Broskoff/Male: IMMUNOLOGy, 4th ed