1. Complement
J. Ochotná

2. Complement humoral component of nonspecific immunity
helps remove microorganisms and own altered cells (apoptotic cells)
complement proteins are synthesized in the liver, less by tissue macrophages and fibroblasts

3. Complement system of about 30 serum and membrane proteins
complement components are present in serum in inactive form
complement activation has cascade character

4. Complement
the main complement components: C1-C9 (C3 is the central component)
other complement components: factor B, factor D, factor P
regulatory proteins: C1 - inhibitor, factor I, factor H, C4bp, DAF, MCP, CR1, factor S (vitronectin), CD59 (protektin), anaphylatoxin inactivator

5. Pathways of complement activation
Riedemann N.C.
Classical pathway
Alternative pathway
Lectin pathway

6. Classical and alternative pathway

7. Complement activation and efector functions

8. Complement regulation and protection of own cells
Activation of complement cascade is controlled by the plasma and membrane inhibitors.
Anaphylatoxin inactivator
DAF
Protectin
MCP

9. Complement regulation
C1 inhibitor (C1-INH) – inhibits C1; if missing→ HAE
factor I with cofactors: MCP (membrane cofactor protein), CR1, factor H – C3b, C4b cleavage
DAF (decay-accelerating protein)-degradation of C3 and C5 convertase

10. Complement regulation
factor S (vitronectin) – inhibits complex C5bC6
CD 59 (protectin) - prevents the polymerization of C9
anaphylatoxin inactivator (CPN)- inactivates anafylatoxins (C3a, C4a, C5a)

11. Complement receptors Bind fragments of complement components
CR1 - on various cells
- promotes C3b, C4b decay
- stimulate phagocytosis erythrocyte transport of immunecomplexes
CR2 - on B lymphocytes and FDC activation of B cells

12. Anaphylatoxin receptors
Complement receptors
CR3, CR4 - on phagocytes participation in opsonization, adhesion
Anaphylatoxin receptors
C3aR, C5aR – receptors for anaphylatoxins mast cell activation

13. Biological significance
Opsonization (C3b, C4b)
Chemotaxis (C3a, C5a)
Osmotic lysis (MAC C5b-C9)
Anaphylatoxins (C3a, C4a, C5a)

16. Basophils and mast cells and their importance in immune responses

17. Mast cells
Mucosal mast cells - in the mucous membranes of respiratory and gastrointestinal tract, produce histamine, serotonin, heparin, tryptase, leukotriene C4 ..., participate in parasitosis and allergy
Connective tissue mast cells – in the connective tissue, producing tryptase, chymase, prostaglandinD2 ..., are multiplicated in fibrosis, in parasitosis and allergy are not participating

18. Mast cell functions Defense against parasitic infections
In pathological circumstances, responsible for the early type of hypersensitivity (immunopathological reaction type I)
Apply during inflammation, in angiogenesis, in tissue remodeling

19. Mast cell activation Mast cells can be stimulated to degranulate by:
cross-linking of IgE receptors (FcRI)
anafylatoxins (C3a, C4a, C5a)
TLR

20. Mast cell activation by cross-linking of IgE Fc receptors
Binding of IgE to highaffinnity Fc receptor for IgE (FcRI)
Binding of multivalent antigen (multicellular parasite) to IgE
Aggregation of several molecules of FcRI

21. Mast cell activation
Mast cell degranulate (cytoplasmic granules mergers with the surface membrane and release their contents)
Activation of arachidonic acid metabolism (leukotriene C4, prostaglandin D2)
Start of production of cytokines (TNF, TGF, IL-4, 5,6 ...)

22. Secretory products of mast cells
Cytoplasmatic granules: hydrolytic enzymes, histamine, heparin, chondroitin sulphate, serotonin Histamine - vasodilation, ↑ vascular permeability (erythema, edema, itching), bronchoconstriction, ↑ intestinal peristalsis, ↑mucus secretion in the respiratory tract and GIT (helps eliminate the parasite)
Arachidonic acid metabolites (leukotriene C4, prostaglandin D2)
Cytokines (TNF, TGF , IL-4, 5,6 ...)

23. Basophils Differentiate from myeloid precursor
Receptor equipment, content of granules, the mechanisms of stimulation and functions are very similar to mast cells
Play a role in parasitic infections and allergies
Basophil activation markers: CD 63, (CD 203)

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

25. Inflammation
Is a protective physiological response leading to protection against infection in damaged sites, localization of damage, elimination of necrotic cells and tissue repair.

26. Local body's response to inflammation Classical signs - pain (dolor), fever (calor), redness (rubor), swelling (tumor)

27. Inflammation
The first signals for the development of inflammatory response come from mast cells, phagocytes, and the substances released from damaged cells and components of extracellular matrix.
With longer duration of local inflammation are activated an antigen-specific mechanisms (T and B lymphocytes).

28. Inflammation

29. Inflammation – local reaction
vasodilation, ↑ vascular permeability (histamine, serotonin, bradykinin, complement components C3a, C5a, leukotrienes , prostaglandins, …) → rednes, swelling
↑expression of adhesion molecules on endothelia (TNFa, IL-1) → leukocyte adhesion to the endothelium
influence of local nerve endings via prostaglandins → pain
Increased local temperature (IL-1, IL-6, TNF, prostaglandins)

30. Inflammation - systemic reaction
Leukocytosis
Fever (TNF, IL-1, IL-6, IFN )
↑ tissue metabolism ↑ mobility of leukocytes ↑ formation of IFN, cytokines, Ig ↑ expression of Hsp
Acute phase proteins (IL-6, TNFa, IL-1) CRP, SAP - opsonization and complement activation

31. Inflammation - systemic reaction
Septic shock - the massive penetration of microorganisms into the bloodstream (TNF)
Anaphylactic shock - basophil and mast cells activation with allergen (histamine)

32. Tissue repair elimination of damaged cells with phagocytes
activation of fibroplastic mechanisms
activation of angiogenesis
regeneration and tissue remodeling
TGF b

33. Antigens

34. Antigen (immunogen) substance which provokes specific immune response
usually proteins or polysaccharides (lipids and nucleic acids only in the combination with proteins or polysaccharides)
molecules > 5 kDa (optimal size of the antigen molecules is about 40 kDa)

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

36. Epitope (antigenic determinant)
part of the antigen which is recognized by immune system (lymphocytes- BCR, TCR, Ig)
cross-reactive antigens - share one or more identical or similar epitopes

37. 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

38. Antigen endogenous antigens - autoantigens (self Ag)
exogenous antigens - foreign substances from the environment
allergen is exoantigen that in the susceptible individuals can cause pathological (allergic) immune response

39. Properties of antigen immunogenicity
proteins> carbohydrates> macromolecule complexes (glycoproteins, nucleoproteins, and glycolipids)> lipids
specificity

40. Factors affecting immunogenicity
Physical: solubility - insoluble Ag more immunogenic molecular weight - ideal 5-40 kDa
Chemical: structure - the number of determinants degradability - "ease" of uncovering the determinants in antigen presenting cells (APC cell)

41. Properties of antigen
Biological: biological heterogeneity genetic and physiological disposition of the body

42. Degree of foreignness Autogeneic - antigens of the same individual
Syngeneic - antigens of genetically identical individuals (eg twins)
Allogeneic (alloantigens) - antigens genetically different individuals of the same species
Xenogeneic (heterologous) - antigens derived from individuals of different species (eg monkey kidney transplant man)

43. Types of antigens according to antigen presentation
T- dependent antigens
T- independent antigens

44. Thymus dependent antigens
more frequently, mostly protein Ag
for specific humoral immune response to antigen is necessary assistance of TH lymphocytes (or response isn´t enough effective)
assistance implemented in the form of cytokines produced by TH lymphocytes

45. T- independent antigens
can stimulate B cells directly
mainly bacterial polysaccharides, lipopolysaccharides and polymer forms of proteins (e.g. Haemophilus, Str.pneumoniae)

46. T-independent pathway

47. Superantigens stimulate T cells polyclonaly and massively
(massive cytokine release)
massive activation of T cells can cause shock
e.g. bacterial toxins (Staph.aureus, Str.pyogenes, Pseud.aeruginosa)

48. 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)

49. Differcence between antigen and superantigen binding

50. Sequestered antigens
autoantigens, that are normally hidden to immune system and therefore unknow (e.g. brain, the lens of the eye , testes)
if they are "uncovered" by demage, exposed to the immune system, are recognized as foreign (one of the theories of autoimmune processes)

51. Immunologically privileged sites
brain, eye, gonads
are protected from potentially damaging inflammatory immune responses
this tissues are far less rejected in allogeneic transplant (cornea)
this privileged position is not absolute

52. Immunologically privileged sites
Mechanisms of protection from the immune system:
isolation from the immune system (blood-brain barrier)
preferences of Th2 and suppression of Th1-response
production of immunosuppressive cytokines (TGFβ)
FasL expression -active protection against effector T-lymphocytes
increased expression of membrane complement inhibitors

53. Thank you for your attention

54. Complement – clasical pathway https://www. youtube. com/watch
Complement – alternative pathway
Mast cells
Acute inflammation