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21. Immune mechanisms of inflammation (local and systemic reaction).

Explore the immune mechanisms of inflammation, causes, acute and chronic responses, local vs systemic effects, cytokine regulation, acute phase proteins, and the repair process of damaged tissues.

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21. Immune mechanisms of inflammation (local and systemic reaction).

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  1. 21. Immune mechanisms of inflammation (local and systemic reaction). 22. Physiological mechanisms of regulation of the immune system. Cytokines (classification according to the function). 23. Defence against extracellular pathogens . 24. Defence against intracellular . 25. Anti-viral defence. 26. Defence against multicellular parasites.

  2. Inflammation

  3. Inflammation Is a physiologicalresponse oftheorganismto harmfulstimuli, leading to localizationofdamage, eliminationofpathogens, necroticcells… and initiationtissuerepairing.

  4. Causes of inflammation • Physicalinjury • Infection by pathogens • Damagecaused by chemicals • Cancer • Alergicdisease • Autoimmunedisease

  5. Inflammation Inflammation acute(physiological reactions, damaged tissue heals completely) chronic(usually pathological reactions, destruction of tissue and compensation with fibrous tissue) Response of the organism local systemic

  6. Local body's response to inflammationSigns - pain (dolor), heat (calor), redness (rubor), swelling (tumor)

  7. Local inflammation The first signals for the development of inflammatory reactions originate from activated phagocytes, mast cells, complementand substances released from damaged cells and extracellular matrix components.

  8. Local inflammation

  9. Local inflammation • vasodilation and increased vascular permeability (histamine, serotonin, bradykinin, complement components C3a, C5a, leukotrienes, prostaglandins) => redness and swelling • increased expression of adhesion molecules on endothelial cells (TNF, IL-1) => capture leukocytes and phagocytes • influence nociceptors (prostaglandins, ...) => pain • Increase temperature (IL- 1, IL-6, TNF, prostaglandins)

  10. Systemic inflammation • leukocytosis • fever (TNFa, IL-1, IL-6, IFN) • ↑ tissue metabolism • ↑ mobility of leukocytes • ↑ IFN, cytokines and Ig production • ↑ expression of Hsp • acute phase proteins (IL-6, TNF, IL-1)

  11. Acute phase proteins produced by hepatocytes: • CRP - opsonization, complement activation • SAP - opsonization, complement activation • SAA - attracting leukocytes • C3, C4 • protease inhibitors - protection against secondary tissue damage • serum transport proteins

  12. Systemic inflammation Septicshock - themassivepenetrationofmicroorganismsintothebloodstream (  TNF) Anaphylacticshock - basophildegranulationaftercontactwithallergen(histamin)

  13. Repair of damaged tissue • after the elimination of pathogens and damaged cells by phagocytes • activation of angiogenesis • regeneration and tissue remodeling (fibroblasts, smooth muscle cells, keratinocytes, epithelial cells) • regulated by cytokines: PDGF, TGFb (platelets, macrophages ...)

  14. Physiological regulation of the immune system

  15. Physiological regulation of the immune system • Regulation by antigen • Regulation by antibodies • Regulation by cytokines and cellular contact • Suppression mediated by T cells • Other factors influencing the outcome of the immune response • Regulation by cytokines

  16. Regulation by antigen • Immune responses induction and extinction • Affinity maturation of B lymphocytes • Maintaining immunological memory • Antigenic competition • Threshold density of the complex MHC II-gp Ag on APC

  17. Regulation by antibodies • Antibodies competes with the BCR for antigen (negative regulator of B lymphocyte stimulating) • IgG immune complexes bind to the BCR and FcgR on B cells, resulting in blocking of B cell activation • Regulation via idiotypic network

  18. Regulation by cytokines and cellular contact • Interaction APC - T lymphocyte • Interaction TH1 – macrophages • Interaction TH2 - B lymphocytes • Mutual regulation of activity TH1 versus TH2 • Development of leukocyte subpopulations Negative regulation of effector cells: • CTLA-4 - T cell inhibitory receptor, binds ligands CD80 and CD86 • Inhibitory receptors of NK cells • Self-destruction interaction of the apoptotic receptor Fas with ligand FasL on the surface of activated T lymphocytes

  19. Suppression mediated by T cells • Mutual negative interactions mediated by Th1 and Th2 cytokines (Th2 cells produce IL-4 and IL-10 which suppress the immune response, based on TH1 cells) • Clonal elimination or anergition of T cells after antigen recognition on the surface of other cells than APC (lacking co-stimulatory signals) • Regulatory T cells maintain tolerance to autoantigens (Treg, Tr1)

  20. Factors influencing the outcome of the immune response Thesame antigen caninduceanactiveimmune response oranactivestateof tolerance, theresultof response depends on many factors: • Stateoftheimmunesystem • Propertiesof antigen • Doseof antigen • Routeof antigen administration

  21. Cytokines (Tissue hormones)

  22. Cytokines • Regulatory proteins and glycoproteins produced by leukocytes and other cells • Essential regulators of the immune system • Apply outside the immune system (angiogenesis, tissue regeneration, carcinogenesis, treatment of many brain functions, embryonic development ...) • Cytokines - secreted      - membrane (CD 80, CD86, CD40L, FasL ..)

  23. Cytokines • 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)

  24. Distribution of cytokines by function • Proinflammatory cytokines (IL-1, IL-6,IL- 8,IL- 12,IL- 18, TNF) • Antiinflammatory cytokines (IL-4, IL-10, TGF) • Cytokines with the activity of hematopoietic cells growth factor (IL-2, 3, 4, 5, 6, 7, 9, 11, 14, 15, CSF, SCF, LIF, EPO) • Cytokines applying in TH2 humoral immunity (IL-4, 5, 9, 13) • Cytokines applying in the cell-mediated immunity TH1 (IL-2, 12, IFN, GM-CSF, lymphotoxin) • Cytokines with antiviral effect (IFN-, IFN-, IFN- )

  25. Overview of the most important cytokines MF – macrophages; M – monocytes; N – neutrophils; DC – dendritic cells; NK – natural killers; L – lymphocytes; B – B cell; T – T cell

  26. Cytokine receptors • Consistingof 2 or 3 subunits • Onesubunitbindscytokine, other are associatedwithcytoplasmicsignalingmolecules (protein kinases) • Signalingsubunitisshared by severaldifferentcytokinereceptors - called receptor family • Signalingthrough these receptorsmaylead to proliferation, differentiation, activationofeffectormechanismsorblockingthe cell cycleandinductionofapoptosis

  27. Defense against extracellular pathogens

  28. Defence against extracellular pathogens • bacteria (gram-negative, gram-positive cocci, bacilli), unicellularparasites • pathogensinduceinflammation • removed by phagocytosis - neutrophilgranulocytes • opsonization (IgGandIgAantibodies, C3b, lectins, CRP...)

  29. Defence against extracellular pathogensOpsonisation and phagocytosis

  30. Defence against extracellular pathogens • Phagocytes are attracted to thesiteofinfection by chemotacticsubstances(C5a, C3a andchemotacticproductsofbacteria…) • ingestedbacteria are destroyed by themicrobicidalsystems(productsof NADP-H oxidase, hydrolyticenzymesandbactericidalsubstances in lysosomes) • phagocytesproduceproinflammatorycytokines(IL-1, IL-6, TNF)

  31. Defence against extracellular pathogens • IgM - complement activation • IgG - activation of complement, opsonization • IgA - opsonizationsIgA prevents against infection by intestinal and respiratory bacteria • in the defense against bacterial toxins apply neutralizing antibodies (Clostridium tetani and botulinum …)

  32. Defence against extracellular pathogens • "indirect toxins - bacterial Lipopolysaccharide (LPS) stimulates big number of monocytes to release TNF, which can cause septic shock • individuals with immunodeficiency of phagocytes, complement and antibodies production are especially at risk of infections with extracellular bacterial

  33. Defense against intracellular pathogens

  34. Defense against intracellular pathogens • bacteria, fungi and unicellular parasites • intracellular parasites are resistant to the microbicidal mechanisms of phagocytes • macrophages, which absorbed them, produce IL-12 → TH1 differentiation, production of IFNg and membrane TNF → activation of macrophages and production of NO

  35. Defense againstintracellularpathogens

  36. Defense against intracellular pathogens • TClymphocytesapply in the defense againstintracelularparasites, whichescapefromphagolysosomes • individualswithcertaindisordersofphagocytesanddefectsof T lymphocytes are at risk ofinfectionswithintracellularmicroorganisms

  37. Defense against intracellular pathogens

  38. Anti-viral defense

  39. Anti-viral defence • interferons - productionofIFNaandIFNbisinduced in infectedcells; IFNgactivatesmacrophages (iNOS) • IFNaandIFNb -preventsviralreplication - induceproliferationofNK cells - increase the expression of HLA-I

  40. Anti-viral defence - interferons

  41. Anti-viral defence • NK cells - ADCC (Antibody-dependent cell-mediated cytotoxicity); NK cell bind with CD16 (Fcg receptor) to IgG which has bound to the surface of infected cell and then NK cell release perforins and granzymes (degranulation) • infected macrophages produce IL-12 (a strong activator of NK cells)

  42. Anti-viral defence - NK cell activation ADCC

  43. Anti-viral defence • in the defense againstcytopathicvirusesappliedantibodies: • sIgAinhibitmucosaladhesionofviruses (defense againstrespiratoryvirusesandenteroviruses) • neutralizingIgGandIgMantibodiesactivatetheclassicalpathwayofcomplement, thatisable to lyse certainviruses • opsonizedviralparticles are phagocytosed • IgAandIgGhavepreventiveeffect in secondaryviralinfection

  44. Anti-viral defence - antibodies

  45. Anti-viral defence • effector TC lymphocytes destroy infected cells in direct contact (granzym/perforin; FasL) and by produced cytokines (lymfotoxin) • some viruses after infection integrate into the host genome, where persist for years (varicella zoster, EBV, papillomavirus) • individuals with T lymphocyte immunodeficiency and with combined immune disorders are at risk by viral infections • increased susceptibility to herpes infections in individuals with dysfunction of NK cells

  46. Anti-viral defence – NK cells and Tc lymphocytes

  47. Defense against multicellular parasites

  48. Defense against multicellular parasites • IgE, mast cells, basophils and eosinophils • TH2 stimulation under the influence of IL-4 (mast cells and other APC stimulated by parasite) • TH2 stimulate B cells with BCR-specific parasite antigens • isotype switching under the influence of IL-4 to IgE • IgE bind to FceRI on mast cells and basophils

  49. Defense against multicellular parasites • multicellular parasite binds to IgE on mast cell→cross-linkingofseveralmoleculesFcRI • initiate mast cell degranulation (releaseofhistamin, tryptase, serotonin…) • activationofarachidonicacidmetabolism(leukotriene C4, prostaglandin PGD2) - amplificationofinflammatoryresponses • cytokineproductionby mast cell (TNF, TGF, IL-4, 5, 6)

  50. Defense against multicellular parasites Histamine • vasodilatation, increase vascular permeability (erythema, edema, itching) • bronchoconstriction (cough) • increases intestinal peristalsis (diarrhea) • increased mucus secretionThis helps eliminate the parasite.

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