Summary The main function of the immune system
- Slides: 40
Summary
The main function of the immune system • Defense • Autotolerance • Immune supervision • Antigens • Exoantigeny (allergens, superantigeny. . . ) • autoantigens • Epitope
Nonspecific immune mechanisms • non-adaptive, congenital • evolutionarily older • respond to the presence of harmful substances quickly • recognize structural features common to many pathogens • absence of immunological memory • components - cellular (phagocytes, NK cells) - humoral (complement, interferons, lectins and other serum proteins)
Specific immune mechanisms • adaptive • evolutionarily younger • antigen specific • Immunological memory • components - humoral (antibody) - cellular (T lymphocytes)
Components of the immune system • lymphoid tissues and organs • cells of the immune system • molecules of the immune system Lymphoid tissues and organs • primary lymphoid organs (bone marrow, thymus) • secondary lymphoid tissues and organs (spleen, lymph nodes and their organized clusters, MALT) • lymphoid organs are connected with other organs and tissues by network of lymphatic and blood vessels
Leukocyte surface molecules • CD nomenclature - a designation surface molecules of leukocytes, a newly described molecules receive serial numbers, some have alternative names associated with their structure or function (eg, CD 14 - LPS receptor, CD 16 -Fcg. RIII. . . ) • antigen-specific receptors (TCR, BCR) • adhesion molecules (integrins, selectins, adhesion molecules Ig-family) • Fc receptors • complement receptors • cytokines and chemokines receptors • MHC gp. • receptors for microbial components. . .
Molecules of the immune system • antigen-specific receptors (TCR, BCR) • antibodies • MHC gp. I. and II. class (HLA) • Fc receptors • adhesion and costimulating molecules • cytokines and their receptors • nonspecific receptor for components of microbial surfaces • complement system
Phagocytes • phagocytosis - absorbing particles from the surroundings • professional phagocytes (neutrophils, eosinophils, monocyte and macrophages) • granulocytes - defense against extracellular pathogens • macrophages - elimination of apoptotic cells, defense against intracellular parasites Receptors of phagocytes • surface lectins - bind microbial glycoproteins and polysaccharides - galactose receptor, manose receptor • CD 14 - binds bacterial LPS • TLR - bind bacterial lipopolysaccharides, lipoproteins, DNA • Scavenger-receptors recognize apoptotic cells • Fc receptors • complement receptors
• opsonization - Ig - complement component - serum MBL - fibronectin, fibrinogen - CRP, serum amyloid P • liquidation of absorbed microorganisms: - lysosomes: bactericidal substances and hydrolytic enzymes - activation of NADPH oxidase - oxidation flash - NO
Mast cells - defense against parasitic infections - in the pathological circumstances are responsible for the early type hypersensitivity
Complement • system of about 30 serum and membrane proteins • main components C 1 -C 9 • cascade activation • MAC (C 5 b, C 6, C 7, C 8 and C 9) • main functions of complement: opsonization (C 3 b) chemotaxis (C 3 a, C 5 a) osmotic lysis (MAC) anafylatoxins (C 3 a, C 4 a, C 5 a) •
• complement activation: an alternative pathway classical pathway lectine pathway • terminal lytic phase of complement cascade → MAC → pores in the membrane → osmotic cell lysis • regulation of complement and protection of its own cells - using membrane and serum proteins - C 1 inhibitor - DAF (decay-accelerating factor) - degradation of C 3 convertase - factor I, MCP (membrane cofactor protein), CR 1, factor H - cleavage of C 3 b - CD 59 (protectin) - prevents the polymerization of C 9
Antigen-specific receptors TCR - antigen recognition module associated with the CD 3 complex - coreceptors CD 4, CD 8 - costimulating receptor CD 28 BCR - surface immunoglobulin (Ig. M, Ig. D) associated with CD 79 a and CD 79 b - costimulating receptor CD 40 - enhanced signaling through CR 2 (CD 21)
Secreted immunoglobulins • structure: - 2 heavy (H) chains - covalently linked by disulfide bonds - 2 light (L) chains - linkeded to the heavy chains by disulfide bonds • isotypes of immunoglobulins: Ig. M, Ig. D, Ig. G (1 -4), Ig. A (1 -2), Ig. E • functions: opsonisation, neutralisation, activation of complement
- pleiotropic effect - operates in a cascade - cytokine network - cytokine system is redundant effects of cytokines - autocrine - paracrine - endocrine - are known as interleukins (exception: TNF, lymphotoxin, TGF, interferons, CSF and growth factors)
Cell-mediated immune mechanisms
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