1. Physiological mechanisms of regulation of the immune system

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

3. 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 activation of B lymphocytes
Regulation via idiotypic network

4. 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

5. T cell: TCR - antigen-specific receptor
Regulation by cytokines and cellular contact Interaction between APC and T cell
T cell: TCR - antigen-specific receptor
CD4 or CD8 - coreceptor (MHCgp binding)
CD 28 - costimulatory receptor (binds CD 80, CD 86)
CTLA-4 - inhibitory receptor (binds CD 80, CD 86)

6. Regulation by cytokines and cellular contact Interaction between TH1 and TH2 cells

7. Negative regulation of effector cells
CTLA-4 - T cell inhibitory receptor, binds ligands CD80 and CD86
Self-destruction interaction of the apoptotic receptor Fas with ligand FasL on the surface of activated T lymphocytes
Inhibitory receptors of NK cells

8. Suppression mediated by T lymphocytes
Mutual negative interaction TH1 and TH2 cytokine-mediated
Clonal elimination or anergy of T lymphocytes after contact with antigen on the surface of other cells than APC
Regulatory T cells (Treg, Tr1, Th3 - CD 4+) help to maintain tolerance to autoantigens; produce TGFb, IL-10

9. Factors influencing the outcome of the immune response
The same antigen can induce an active immune response or an active state of tolerance, the result of response depends on many factors:
State of the immune system
Properties of antigen
Dose of antigen
Route of antigen administration

10. Cytokines (Tissue hormones)

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

12. Cytokines Pleiotropic effect Operates in a cascade Cytokine network
Cytokine system is redundant
Effects of cytokines - autocrine paracrine endocrine
Are known as interleukins (IL-1…IL-38) (except: TNF, lymphotoxin, TGF, interferons, CSF and growth factors)

13. B cells communicate via cytokines with other cells, such as T cells and macrophages

14. Overview of the most important cytokines
Produced
Function
IL-1
MF, N
T cell costimulation, induction of TNF and IL-8, pyrogen
IL-2
Th1
Growth factor for T cells
IL-4
Th2, basophils
Th2 differentiation, B cell stimulation, isotype switching to IgE and IgG4, Th1 inhibition
IL-5
Th2, eosinophils
B cell stimulation, growth factor for eosinophils
IL-6
Th2, MF, N
T and B cell stimulation, stimulation of Ig production, induction of acute phase proteins synthesis, pyrogen
IL-8
MF, other cells
Granulocyte activation and chemotaxis (primarily neutrophils)
IL-10
Th2,M, Treg
Th1 and MF inhibition, B cell differentiation to plasma cell
IL-12
MF, DC, B
Th1 differentiation, NK stimulation
TNF
M, MF, NK
Induction of local inflammation, endothelium activation, induction of apoptosis
TGFb
T, MF, platelets
The anti-inflammatory effect (control of lymphocyte proliferation, control of Ig production, control MF activity), stimulation of fibroblasts and osteoblasts, gain production of extracellular matrix
IFNa
L, M, MF
Inhibition of viral replication
IFNb
Fibroblasts, epithelial cells
IFNg
Th1, NK
MF activation, stimulation of MHC gp. expression, Th2 inhibition
MF – macrophages; M – monocytes; N – neutrophils; DC – dendritic cells; NK – natural killers; L – lymphocytes; B – B cell; T – T cell

15. Clasification of cytokines by functions
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 anti-viral effect (IFN-, IFN-, IFN- )

16. Cytokine receptors Consisting of 2 or 3 subunits
One subunit binds cytokine, other are associated with cytoplasmic signaling molecules (protein kinases)
Signaling subunit is shared by several different cytokine receptors - called receptor family
Signaling through these receptors may lead to proliferation, differentiation, activation of effector mechanisms or blocking the cell cycle and induction of apoptosis

17. Possibilities of therapeutic affecting of the immune system

18. Causal treatment a) Stem cell transplantation
treatment of severe congenital disorders of the immune system and some lymphoproliferative and myeloproliferative disorders
complications: infectious complications                     Graft-versus-host disease
obtaining stem cells - from bone marrow                              - from umbilical cord blood                              - from peripheral blood

19. Causal treatment b) Gene therapy
transduction of the missing gene to hematopoietic stem cells using viral vectors
used as a treatment for 2 forms of SCID

20. Substitution treatment
autologous stem cell transplantation (following chemotherapy and radiotherapy)
treatment with intravenous immunoglobulin (derived from plasma of blood donors)
substitution of C1 inhibitor for hereditary angioedema
substitution of erythropoietin in patients with chronic renal failure
substitution of G-CSF in agranulocytosis

21. Non-specific immunosuppression
Immunomodulation
= medical procedure to adjust the disrupted immune function
Non-specific immunosuppression
nonspecific = affects not only autoreactive and aloreactive                        lymphocytes, but also other components of immunity (risk of reduction antiinfectious and antitumor immunity)
used for treatment of autoimmune diseases, for organ transplantation and severe allergic conditions

22. Non-specific immunosuppression
Corticosteroids
anti-inflammatory, immunosuppressive effects
suppress the expression of some genes (IL-2, IL-1, phospholipase A, MHC gp II, adhesion molecules)
inhibition of histamine release from basophils
higher concentrations induce apoptosis of lymfocytes

23. Non-specific immunosuppression
Immunosuppressants affecting the metabolism of DNA (cytostatics)
cyclophosphamide (alkylating agent)
methotrexate (antimetabolite)
azathioprine (purine analogue)

24. Non-specific immunosuppression
Immunosuppressant selectively inhibiting T cells
immunosuppressive ATB: cyclosporine A, tacrolimus, rapamycin (suppressing the expression of IL-2 and IL-2R in activated T lymphocytes)
anti-CD3 monoclonal antibody (imunosuppression after transplantation, treatment of rejection crises)

25. Non-specific immunosuppression
Immunoglobulins in the immunosuppressive indication
polyspecific intravenous immunoglobulins
inhibition of B lymphocytes
antiidiotype activity
inhibition of cytokines
neutralization of toxins
inhibition of complement activation

26. Anti-inflammatory and antiallergic treatment
nonsteroidal anti-inflammatory drugs
antihistamines - blocking H1 receptor                           - reduce the expression of adhesion molekules                           - reduce the secretion of histamine ...
inhibitors of inflammatory cytokine monoclonal antibodies against TNF                           thalidomide (TNF inhibitor)
Anti IgE antibodies (omalizumab)
- severe allergic astma

27. Non-specific immunostimulant therapy
synthetic immunomodulators
Methisoprinol (Isoprinosine) - used in viral infections with more severe or relapsing course
bacterial extracts and lysates
Broncho-Vaxom - prevention of recurrent respiratory tract infections
Ribomunyl
products of the immune system
IL-2 - renal adenocarcinoma
IFNa, IFNb - viral hepatitis, some leukemia
Erythropoietin – renal failure
G-CSF, GM-CSF – neutropenia
Transfer factor (blood donors leukocytes undergoing dialysis)
Thymus hormones               

28. Antigen-specific immunomodulation
specific immunomodulation = induce of an immune response or tolerance to a specific antigen
active immunization
passive immunization
specific immunosuppression

29. Antigen-specific immunomodulation
Active immunization (vaccination) = the induction of immunity after exposure to an antigen
activates specific cellular and humoral immunity
creates long-term immunity (memory cells)
protect against a pathogen bearing this antigen or similar antigen (prophylaxis)

30. Antigen-specific immunomodulation
active immunization (vaccination)
vaccines are made from inactivated or attenuated microorganisms or their antigens (polysaccharide capsule, toxins)
attenuated vaccines cannot be used by immunocompromised individuals
risk of infection or anaphylactic reactions

31. Antigen-specific immunomodulation
Passive immunization
natural - transfer of maternal antibodies in fetal blood
therapeutically - the use of animal antibodies against various toxins (snake toxins, tetanus toxin, botulinum toxin)
prophylaxis - the human immunoglobulin from immunized individuals (hepatitis A, rabies, tetanus)
                    - Anti-RhD antibodies – prevent immunization of mother with RhD+ fetus erythrocytes
provides a temporary (3 weeks) specific humoral immunity
the risk anaphylactic reactions

32. Antigen-specific immunomodulation
Specific immunosuppression = induction of tolerance to a specific antigen
induction of tolerance by oral administration of antigen (treatment of certain autoimmune diseases)
allergen immunotherapy (pollen, insect poisons)
Vaccination against cancer
immunization by dendritic cells

33. Antiinfection immunity

34. Defence against extracellular pathogens
bacteria (gram-negative, gram-positive cocci, bacilli), unicellular parasites
pathogens induce inflammation
removed by phagocytosis - neutrophil granulocytes
opsonization (IgG and IgA antibodies, C3b, lectins, CRP...)

35. Defence against extracellular pathogens Opsonisation and phagocytosis

36. Defence against extracellular pathogens
Phagocytes are attracted to the site of infection by chemotactic substances (C5a, C3a and chemotactic products of bacteria…)
ingested bacteria are destroyed by the microbicidal systems (products of NADP-H oxidase, hydrolytic enzymes and bactericidal substances in lysosomes)
phagocytes produce proinflammatory cytokines (IL-1, IL-6, TNF)

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

38. 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

39. Defense against intracellular pathogens

40. 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

41. Defense against intracellular pathogens

42. Defense against intracellular pathogens
TC lymphocytes apply in the defense against intracelular parasites, which escape from phagolysosomes
individuals with certain disorders of phagocytes and defects of T lymphocytes are at risk of infections with intracellular microorganisms

43. Defense against intracellular pathogens

44. Anti-viral defense

45. Anti-viral defence
interferons - production of IFNa and IFNb is induced in infected cells; IFNg activates macrophages (iNOS)
IFNa and IFNb - prevents viral replication
- induce proliferation of NK cells
- increase the expression of HLA-I

46. Anti-viral defence - interferons

47. 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)

48. Anti-viral defence - NK cell activation
ADCC

49. Anti-viral defence
in the defense against cytopathic viruses applied antibodies:
sIgA inhibit mucosal adhesion of viruses (defense against respiratory viruses and enteroviruses)
neutralizing IgG and IgM antibodies activate the classical pathway of complement, that is able to lyse certain viruses
opsonized viral particles are phagocytosed
IgA and IgG have preventive effect in secondary viral infection

50. Anti-viral defence - antibodies

51. 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

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

53. Defense against protozoa parasites

54. Defense against protozoa parasites
Toxoplasma gondii, Leishmania, Trypanosoma
defense against protozoa parasites is similar to bacteria
extracellular parasites - antibodies
intracellular parasites - TH1 lymphocytes and activated macrophages

55. Defense against multicellular parasites

56. 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

57. Defense against multicellular parasites
multicellular parasite binds to IgE on mast cell→ cross-linking of several molecules FcRI
initiate mast cell degranulation (release of histamin, tryptase, serotonin…)
activation of arachidonic acid metabolism (leukotriene C4, prostaglandin PGD2) - amplification of inflammatory responses
cytokine production by mast cell (TNF, TGF, IL-4, 5, 6)

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

59. Mast cell activation

60. Defense against multicellular parasites
eosinophils fagocyte complexes of parasitic particles with IgE via their receptors for IgE
eosinophils use against parasites extracellular bactericidal substances released from granules (ECP- eosinophil cationic protein, MBP-major basic protein…)

61. Defense against multicellular parasites - eosinophils

62. Thank you for your attention

63. Phagocytosis https://www.youtube.com/watch?v=7VQU28itVVw