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Immune system

Immune system. J. Ochotná.

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Immune system

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  1. Immune system J. Ochotná

  2. The main functions of the immune systemImmune system belongs to the basic homeostatic mechanisms Defense - identification and protection against pathogenic microorganisms and their toxinsAutotolerance – recognition of own tissues and keeping tolerance to themImmune surveillance - identifying and removing the old , damaged and otherwise changed cells

  3. Antigen (immunogen)* substance that the immune system recognizes and responds to it* usually proteins or polysaccharides (lipids and nucleic acids only in the combination with proteins or polysaccharides)* Molecules <5 kDa can´t trigger an immune response, the optimal size of the antigen molecules to initiate immune response is about 40 kDa*autoantigen - antigen derived from his own body*exoantigen - alien substance from the external environment allergen - exoantigen that in susceptible individuals may cause pathological (allergic) immune response

  4. Haptens * small molecules, that are able to induce specific immune response only after the establishment to the macromolecular carrier (separate haptens are not immunogenic) * typically drugs (eg penicillin antibiotics, hydralazin)

  5. Interaction antigen – antibody * Binding site of antibody (paratop) form non-covalent complexes with the corresponding part on antigen molecule (epitope)* participation: the hydrogen bonds, electrostatic and hydrophobic interactions, van der Waals forces* antigen-antibody complex is reversible

  6. Types of antigens according to antigen presentation1) thymus dependent antigens* more frequently, mostly protein Ag* for specific humoral immune response to antigen is necessary to cooperate with TH lymphocytes (or response isn´t enough effective)* assistance implemented in the form of cytokines produced by TH lymphocytes

  7. Types of antigens according to antigen presentation2) thymus independent antigens* in a small number of antigens can be induced antibodies production directly without the participation of T lymphocytes* this are mainly a bacterial polysaccharides, lipopolysaccharides and polymer forms of proteins (e.g. Haemophilus, Str.pneumoniae)

  8. Superantigens* proteins (microbial products) which have 2 binding sites, one interacts with the epitope presented on all MHCgpII, second interacts with other structures presented in many different TCR molecules (connection of T lymphocyte with APC)* stimulate polyclonaly and massively * massive activation of T lymphocytes can cause shock* e.g. bacterial toxins (Staph.aureus, Str.pyogenes, Pseud.aeruginosa)

  9. Differcence between antigen and superantigen binding

  10. Sequestered antigens*autoantigens that are normallyhidden to the immune system and therefore unknow (e.g. the lens of the eye , testes)* if they are "uncovered" by demage, may take the immune system to respond (one of the theories of autoimmune processes)

  11. Components of the immune system

  12. Components of the immune system* Lymphoid tissues and organs* Cells of the immune system* Molecules of the immune system

  13. Lymphoid tissues and organs* are linked with the other organs and tissues by network of lymphatic and blood vesselsPrimary lymphoid tissues and organs*bone marrow, thymus* place of maturation and differentiation of immunocompetent cells* immature lymphocytes acquire here their antigenic specificity

  14. Secondary lymphoid tissues and organs* meeting place of immunocompetent cells with Agspleen - in contrast to the lymph nodes filter the blood and captures presented antigenslymph nodes and their organized clusters (tonsils, appendix, Peyer patches in the intestine) - filter lymph and capture present antigens MALT (mucous associated lymphoid tissue) - diffuse lymphatic tissue, the main role is capture of antigens that penetrate through the mucous membrane

  15. Cells of the immune system* evolution of red and white blood cells begin at yolk sack, then haematopoiesis travels to fetal liver and spleen (3 to 7 month gestation), the main hematopoietic function has bone marrow* all blood cells arise from a pluripotent stem cell (CD 34)* stem cells are modified and maintained throughout life * haematopoiesis is regulated by cytokines that are secreted by bone marrow stromal cells, activated TH cells and macrophages

  16. Immune mechanisms

  17. Immune mechanismsNonspecific and specific immune mechanisms cooperate with each other. ToleranceRedundancy

  18. Nonspecific immune mechanisms* non-adaptive, innate* evolutionarily older* no immunological memory* in the presence of pathogens react quickly, in minutes (based on molecules and cells which are in the body prepared in advance)* component cellular - phagocytes (some are APC), NK cells humoral - complement, interferons, lectins and other serum proteins

  19. Specific immune mechanisms* adaptive, antigen-specific*evolutionarily younger*have immunological memory*development of a full-specific immune response takes several days even weeks* component cellular - T lymphocytes (TCR) humoral - antibodies

  20. Specific immune mechanismsClonal, anticipatory principle - the immune system is able to predict (anticipate) meeting with any Ag, so that it is prepared to advance a large number of T and B lymphocytes, which differ in their antigen-binding sites of specific receptors (TCR and BCR) and after contact with certain Ag multiply relevant cells and create clones of cells with the same specificityPrinciple of the second signal - for the full activation of lymphocytes is necessary costimulating signal, when it is not present, and lymphocyte reaches only the first signal (via the TCR, BCR), it leads to anergy or apoptosis

  21. Mucosal and skin immune system

  22. Function and structure of the mucosal and skin immune systemMucous membranes and skin are in constant contact with the outside environment, there is concentrated about 80% of immunocompetent cells.Skin - barrier against mechanical, physical and chemical damage, and against the penetration of microorganisms, humans surface of about 1,5 m2Mucosal immune system - prevents the penetration of pathogenic microorganisms, preventing the development of self-harm inflammatory immune responses against pathogens and harmless antigens from the external environment, mucosa with an area of about 400 m2

  23. Natural non-immune protective mechanismsIn protection the body against infection are important intact mucous membranes and skin and nonimmune protective mechanisms.mechanical – movement of cilia, air flow in the airways, or fluid flow in the urinary tractchemicals – fatty acids on skin; lysozyme in saliva, tears and sweat; antibacterial defensins, acid pH in stomach and urinemicrobial - non-pathogenic microflora

  24. Structure of mucosal immune systemMALT (mucous associated lymphoid tissue) BALT (bronchus associated lymphoid tissue)GALT (gut associated lymphoid tissue)NALT (nasal associated lymphoid tissue)o-MALT (organized) – consists from lymphoid follicles in the mucous membrane, tonsil and adenoids, appendix, Peyer patches d-MALT (diffuse) - is made up of leukocytes diffusely distributed in the lamina propria (T and B lymphocytes, macrophages, neutrophils, eosinophils and mast cells)

  25. Intraepithelial T lymphocytes*located predominantly in the villi of the small intestine* mostly have TCRab a coreceptor CD8* produce TGFb (mucosal healing)* suppression of adverse reactions to food allergens

  26. Humoral immune mechanisms of the mucous systemsIgA*(secretory immunoglobulin A)* most significant mucosal immunoglobulin, in breast milk* transcytosis - IgA is transported across the epithelium using transport Fc receptor (poly-Ig receptor), on luminal side is IgA split off with the part of the receptor called secretory component, which protects Ig against intestinal proteases* neutralizing antigens on mucosal surfaces, don´t activate complement, binds to Fc receptors on phagocytes, in Peyerś patches may be immune complexes with IgA captured and can induce immune response

  27. sIgM* secretory immunoglobulin M* applied in newborns and in selective IgA deficiency* more prone to intestinal protease degradation* neutralizing antigens on mucosal surfacesIgG*get on the mucous membrane by diffusion* applies particularly in the lower airways

  28. Induction of mucosal immune responseOral tolerance* majority of antigens given orally causes suppression of specific immunity (critical is also the size of the antigenic particles)*Tr lymphocytes (regulatory) - production of IL-10Induction of mucosal immune response* M cells - specialized enterocytes that provide transport of Ag (endocyte Ag from the surroundings) - are in close contact with lymphocytes and APC* mucosal immunization leads to stimulation of TH2 and TH3 lymphocytes and IgA production

  29. Immunological importance of the breastfeedingBreast milk contains:* sIgA, IgG (neutralization of infectious microorganisms, their products and potential allergens - before the full development of the newborn mucosal immune system)* CD 59 (protektin) - protect cells from the effects of complement* lysozyme, lactoferin, complement components, cytokines, including interferons* immunocompetent cells

  30. Skin immune systemEpidermis*keratinocytes - secretion of cytokines (IL-1,6,TNF,IL-10,TGFb) - expression of MHCgpII → can serve as APC * Langerhans cells - skin dendritic cells (APC)* scattered intraepithelial lymphocytes* melanocytesDermis*fibroblasts - collagen production - removal of apoptotic cells* mast cells* T lymphocytes (small amount)* vessels, hair follicles, sweat and sebaceous glands

  31. Immune mechanisms of inflammation (Local and systemic reactions)

  32. Inflammation * Is a summary of physiological responses to breach the integrity of the organism, leading to protection against infection of damaged sites, localization of damage and healing. * The first signals to the development of inflammatory responses come from mast cells, phagocytes, and the substances released from damaged cells and extracellular components of matter.

  33. Local response to inflammation- increased permeability of blood vessels (vasoactive amines, complement components C3a, C5a, leukotrienes ..., swelling at site of inflammation) - increased expression of adhesion molecules on endothelia - activation of coagulation, fibrinolytic, kinin and complement system - influence of local nerve endings (prostaglandins, pain) - changes in temperature (IL-1, IL-6, TNF, prostaglandins)

  34. Systemic response to inflammation- depends on the extent of damage and duration of local inflammation - fever (proinflammatory cytokines TNF, IL-1, IFN ; stimulate hypothalamic center of thermoregulation) - mobilization of tissue metabolism - induction of expression of Hsp (heat-shock-proteins; function as chaperones) - production of acute phase proteins(CRP, SAP, C4, C5; opsonization and complement activation)

  35. - increased hepatic synthesis of certain serum transport proteins (ceruloplasmin, transferrin) - increased synthesis of protease inhibitors ( macroglobulin) - leukocytosis Septic shock - the massive penetration of microorganisms into the bloodstream (  TNF) Anaphylactic shock - basophil degranulation and complement activation with allergen

  36. Repair of damaged tissue - elimination of damaged cells with phagocytes - activation of fibroplastic mechanisms - activation of angiogenesis - regeneration and tissue remodeling

  37. Phagocytosis

  38. Phagocytosis= ability to absorb particles from the surroundingsProfessional phagocytes* cells, which provide defenses by mechanism of phagocytosis* neutrophilic and eosinophilic granulocytes, monocytes and macrophagesgranulocytes - a defense against extracellular pathogens - able to perform effector functions immediately - neutrophils don´t express MHCgpII (not APC)macrophages - the removal of own apoptotic cells, defense against certain intracellular parasites - fully functional after activating by cytokines (IFNg, TNF)

  39. The intersection of phagocytesin damaged and infected tissues7% of peripheral neutrophils and phagocytes93% neutrophils and phagocytes in the bone marrow* this ratio changes due to inflammatory cytokines and bacterial products* in place of damage are captured phagocytes to endothelium (due to inflammatory cytokine expression of adhesion molecules is higher)* the first is interaction between selectins (adhesion proteins of endothelial cells) and carbohydrate structures on the surface of neutrophils - called roling, which slows the movement of neutrophils

  40. * then there is a stronger link between ICAM-1 (endothelial cells) and leukocyte integrins (neutrophils) or VCAM-1 (endothelial cells) and b1-integrins (monocytes, eosinophils) and subsequent penetration between endothelial cells to the tissue - diapedesis , extravasation* phagocytes are directed to the site of inflammation by chemotactic active substances (IL-8, MIP-1a and b, MCP-1, RANTES, C3a, C5a, bacterial products ...), for which phagocytes have receptors* in tissue phagocytes move so that they secret the hydrolytic enzymes witch cleave components of intercellular substance

  41. Receptors on phagocytesPAMPs - "pathogen associated molecular patterns„ - structures that are located on the surface of microorganisms, but not on their own intact cells* mannose receptor* galactose receptor* CD14 (binds bacterial LPS)* receptors of TLR group (binds bacterial lipoproteins, lipopolysaccharides, bacterial DNA)* scavenger receptors (bind phospholipids on the surface of apoptotic cells)

  42. Opsonization - process, which increases the efficiency of foreign particles phagocytosis - the establishment of opsonins (IgG, IgA, C3b, MBL, fibronectin, fibrinogen, CRP, SAP) on the surface of foreign particles* Fc receptors on phagocytes (recognize antibodies linked to surface of micro-organism)* complement receptors (for binding C3b)

  43. Liquidation of absorbed organism* fusion of fagosome with lysosomeslysosomes contains - bactericidal substances (defensins) - hydrolytic enzymes (cathepsin, lysozyme) - liquid with a pH of 4-5*activation of membrane NADPH oxidase after activation of Fc receptors and complement receptors, which leads to respiratory (oxidative) flash, when arise reactive oxygen intermediates (superoxid radical O2-, singlet oxygen, hydrogen peroxide, hydroxyl radical), which damage the structure of biopolymers, enzymes and DNA of microorganisms;enzyme myeloperoxidase catalyses the reaction of H2O2 withCl- to form chlornan anions (ClO-)* creation of nitric oxide (NO), which produces NO synthase of macrophages after activation with cytokines (IFNg, TNF) that are produced by TH1 lymphocytes, NO liquidate intracellular parasites of macrophages

  44. Secretory products of phagocytes* IL-1, 6, TNF (systemic response to inflammation)* IL-8 (chemokine)* IL-3, GM-CSF (control haematopoiesis)* TGFa, TGFb (helping healing of tissues)* metabolic products of arachidonic acid (prostaglandins, prostacyclin, leukotrienes and thromboxanes

  45. Complement

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