1. DEFINITION AND PROPERTIES OF ANTIGEN
IMMUNOLOGICAL DEFINITION
Any chemical structure
Soluble or corpuscle
Simple or complex
Originated from the body or comes from outside
Genetically self or non-self
Natural or artificial

2. DEFINITIONS
ANTIGEN (Ag) - any substance, which is recognized by the mature immune system of a given organism
ANTIGENICITY– capability of an antigen to bind specifically with certain product of the adaptive immunity: TCR or BCR/antibody,
immunogenicity - capability of an antigen to induce an (adaptive) immune response,
tolerogenicity - capability to induce immunological tolerance, specific immune non-responsiveness

3. FACTORS INFLUENCING IMMUNOGENICITY I.
Foreignness
Size
Genetics
Species
Individual
Age
Dose
Route subcutaneous > intravenous > oral / intranasal Not true for live vaccines (i.e. oral polio vaccine)
Foreignness: evolutionary the farther the species are from each other the more their antigens induce immune response in another
Size: i.e. haptenes (too small to induce immune response without carriers)
Genetics: differences of the immune response between species from the same family/order and between individuals of the same species
Age: the old mainly rely on the immunological memory, they can hardly get over a new kind of infection. Moreover there are differences in the immune response generated by EBV and mumps viruses in childhood and adulthood

4. FACTORS INFLUENCING IMMUNOGENICITY II.
Adjuvant (vaccination)
substances that enhance an immune response to an antigen (aluminum salts, LPS, Freund’s adjuvant, TLR ligands)
complex effects
depot effect – slower biodegradation, prolonged antigen intake by antigen presenting cells
activation of innate immunity
Physical status
corpuscle (cell, colloid) or soluble
denatured or native
Degradability
antigen presentation by APC

5. ANTIGENIC DETERMINANT (=EPITOPE)
part of the antigen which is recognized by a defined immunoglobulin (BCR / antibody) or by T cell receptor

6. Ig
(antibody)
BCR
(mIg)

7. TYPES (STRUCTURE) OF ANTIGEN DETERMINANTS
linear determinant
conformational determinant
(TCR, BCR, Ig)
(BCR, Ig)
conformational determinant
Ab2
Ab1
surface/accessible determinants
cleveage
denaturation
hidden/revealed determinant
new/neoantigen determinant
conformational/linear determinant

8. B cell epitope T cell epitope recognized by B cells proteins
polysaccharides
lipids
DNA
steroids
etc. (many artificial
molecules)
cell or matrix associated
or soluble
recognized by T cells
proteins mainly
(8-23 amino acids)
requires processing by
APC
Some T cells are able to recognise glycolipids bound to non-conventional MHC molecules (e.g. CD1) too

9. ANTIGEN RECOGNITION ≠ CELL ACTIVATION

10. ANTIGEN RECOGNITION BY NAIVE T CELLS REQUIRES
PRESENTATION VIA MHC MOLECULES
Recognition/
No activation
The mature naive cytotoxic T cells (Tc) activate by recognizing antigens bound to MHC I molecules on the surface of antigen presenting cells (APCs) with the help of costimulatory molecules and then they are able to recognize these antigenes bound to MHC I molecules on the surface of host cells (HC) too.
CD4 is the co-receptor of helper T cells (Th) and CD8 is the co-receptor of the cytotoxic T cells (Tc).
Recognition/
Activation

11. SUPERANTIGENS
Fever
Microbial proteins that bind to and activate all the T cells that express a particular set or family of TCR molecules resulting in a polyclonal activation.
Interaction is not via the peptide binding cleft of MHC molecule.
The superantigens can aspecifically bind to the TCR and MHC molecules thereby stabilizing their connection, resulting in the activation of the T-cell subpopulation
Hypotension
Rash
Desquamation

12. monoclonal/oligoclonal
SUPERANTIGENS
Microbial proteins that bind to and activate all the T cells in an individual that express a particular set or family of TCR molecules
conventional antigen
superantigen
polyclonal
T cell response
1:4 - 1:10
monoclonal/oligoclonal
T cell response
1: :105
activated T cells
107 – 108 / 1011
1010 / 1011

13. SUPERANTIGENS Classification Sources Endogenous Exogenous
Exogenous
1.Mouse mammary tomor virus (MMTV)
Epstein-Barr virus (EBV)
Staphylococcal enterotoxins (SEs): A, B, C1 to C3, D, E, G to Q
Staphylococcal toxic shock syndrome toxin-1 (TSST-1)
Staphylococcal exfoliative toxins: exoliatin A, exfoliatin B
Staphylococcal enterotoxin-like toxins formed due to recombination within enterotoxin gene cluster:
U2, V
Streptococcal pyrogenic exotoxins (SPEs): A1 to A4, C, G to M
Streptococcal mitogenic exotoxins: SMEZ
Streptococcal superantigen :SSA
Yersinia pseudotuberculosis: Yersinia pseudotuberculosis-derived mitogen (YAM)
Mycoplasma species: Mycoplasma arthritidis-derived mitogen (MAM)
Cholera toxin:  subunit A of cholera toxin
Prevotella intermedia*
Mycobacterium tuberculosis*
Viral superantigens:  (a) Mouse leukemia virus
                                        (b) IDDMK1222- Ppol-ENV-U3
                                        (c) HIV-Nef
                                        (d) Rabies virus-nucleoside protein
The superantigens can be broadly classified into following families:
i. Endogenous superantigens: These superantigens are encoded by various viruses integrated into the genome. Examples are superantigens produced by mouse mammary tumor virus (MMTV) and Epstein-Barr virus (EBV) associated superantigen.
ii. Exogenous superantigens: These include the exotoxins secreted by microorganisms. Examples are staphylococcal enterotoxins (A, B, C1 to C3, etc.), streptococcal pyrogenic exotoxins (A1 to A4, C, etc) and others (see Table 1) [7, 12-18].
iii. B-cell superantigens: Those superantigens which stimulate predominantly B cells. Examples include staphylococcal protein A and protein Fv. .

14. T CELL-DEPENDENT B CELL ACTIVATION Polysacharides are not presented!
cytokines
CD4
TCR
MHCII
+peptide
T cell 2 1
Polysacharides are not presented!

15. B CELL ACTIVATION WITHOUT THE HELP OF T CELLS
T-INDEPENDENT ANTIGEN
TI-1
T-INDEPENDENT ANTIGEN
TI-2
B cell
Simultaneous activation of BCR and other receptors on B cells (i.e. LPS binding protein /CD14) induces the B cells to proliferate and differentiate
Strong crosslinking of BCR by repetitive polysaccharide or protein epitopes
B CELL ACTIVATION
(extra activation signal)
(extensive receptor-aggregation)

16. B CELL ACTIVATION WITHOUT THE HELP OF T CELLS
(A lot of small ones or a large with multiple epitopes. Usually the same kind, like polysaccharides.)

17. Microorganisms have several different cell surface epitopes

18. COMPLEX ANTIGENS CONSIST OF THE CARRIER AND MULTIPLE EPITOPES (=ANTIGEN DETERMINANTS)
HAPTEN
substance that is non-immunogenic but which can react with the products of a specific
immune response. Haptens are small molecules which could never induce an immune response
when administered by themselves but which can when coupled to a carrier molecule.
Free haptens, however, can react with products of the immune response after such
products have been elicited. Haptens have the property of antigenicity but not immunogenicity.
Haptenic/antigen determinant (epitope)
part of the antigen which are recognized by a defined immunoglobulin (B cell receptor or antibody) or by T cell receptor
Carrier part of the antigen directly not involved in connection with the defined Ig/BCR or TCR
These terms can only be used to describe the
interaction of particular antigenic determinant
and single immunoglobulin or T cell receptor

19. Antibody response generated against a hapten-carrier conjugate
carrier + hapten
antibodies
Hapten-carrier conjugates have native antigenic determinants of the carrier as well as new determinants of the hapten.
carrier specific
hapten specific
carrier + hapten specific

20. ACUTE INFLAMMATION
AND
ACUTE-PHASE RESPONSE

21. THE INFLAMMATORY RESPONSE
Illustrated here are the events following an abrasion of the skin. Bacteria invade the underlying connective tissue and stimulate the innate immune response.

22. ACUTE INFLAMMATION
Acute inflammation is a rapid response to an injurious agent that serves to deliver mediators of host defense — leukocytes and plasma proteins — to the site of injury.
Vascular phase
Vasoconstrictionvasodilation
Increased permeability  edema, leakage of plasma proteins (acute phase proteins, antibodies)
Cellular phase
Migration of leukocites from the circulation to the site of inflammation
Acute inflammation has three major components:
alterations in vascular caliber that lead to an increase in blood flow
structural changes in the microvasculature that permit plasma proteins and leukocytes to leave the circulation
emigration of the leukocytes from the micro-circulation, their accumulation in the focus of injury, and their activation to eliminate the offending agent

24. CAUSES LEADING TO ACUTE INFLAMMATORY REACTIONS:
Infections (pathogenic microbes and microbial toxins)
Trauma (blunt and penetrating)
Physical and chemical agents (thermal injury e.g. burns or frostbite; irradiation; some environmental chemicals)
Foreign bodies (splinters, dirt, sutures)
Immune reactions (hypersensitivity and autoimmune reactions)
Except for Chuck Norris

25. The classic symptoms of inflammation:
redness (rubor) - vasodilation,
swelling (tumor) - edema,
heat (calor) – increased perfusion,
pain (dolor) – factors stimulating nociceptors,
loss of function (functio laesa)

27. CHEMICAL MEDIATORS OF INFLAMMATION I.
Vasodilation
Prostaglandins (PG..), nitric oxide (NO)
Increased vascular permeability
vasoactive amines (histamine, serotonin), C3a and C5a, bradykinin, leukotrienes (LT..), PAF
Chemotaxic leukocyte activation
C3a, C5a, LTB4, chemokines

28. CHEMICAL MEDIATORS OF INFLAMMATION II.
Fever
IL-1, IL-6, TNF, prostaglandins
Pain
prostaglandins, bradykinin
Tissue damage
neutrophil and macrophage products
lysosomal enzymes
oxygen radicals
nitric oxide (NO)

29. MIGRATION OF NEUTROPHILS
FROM BLOOD
TO INFLAMMED TISSUE

30. MIGRATION OF NEUTROPHILS

31. Neutrophil Transendothelial Migration (Diapedesis)

32. ENDOTHELIAL ADHESION MOLECULES DURING INFLAMMATION
(A) The extent of leukocyte adhesion and expression of adhesion molecules on endothelial cells before and after inflammation. (B) Endothelial adhesion molecules and the moieties to which they bind on leukocytes. (C) The changes over time in expression of particular endothelial adhesion molecules following endothelial stimulation. CHO, Carbohydrate; HIMECs, human intestinal microvascular endothelial cells. Part C Haraldsen G. et al. (1996). Cytokine-regulated expression of E-selectin, intercellular adhesion molecule-1 (ICAM-1), and vascular cell adhesion molecule-1 (VCAM-1) in human intestinal microvascular endothelial cells. With information from The Journal of Immunology 156, 2558–2565.

33. PUS
Pus = transudate (liquor puris) + dead pathogens + dead neutrophils + dead tissue cells
Pus is a whitish-yellow, yellow, or yellow-brown exudate produced by
vertebrates during inflammatory pyogenic bacterial infections. Pus consists of
a thin, protein-rich fluid, known as liquor puris, and dead cells.

34. CONSEQUENCES OF MACROPHAGE ACTIVATION SYNTHESIS OF CYTOKINES

35. ACUTE-PHASE REACTION
proinflammatory cytokines hypothalamic control of body temperature increased ‚set-point’ value fever

36. Mannose binding lectin/protein
ACUTE PHASE REACTION
IL-6
Complement
Liver
C-reactive protein (CRP)
Mannose binding lectin/protein
MBL/MBP
Fibrinogen
Stimulation and synthesis of positive acute-phase reactants during inflammation.
Inflammation caused by infection or tissue damage stimulates the circulating inflammation-associated cytokines, including interleukin-1 (IL-1),
interleukin-6 (IL-6), and tumor necrosis factor (TNF)-. These cytokines
stimulate hepatocytes to increase the synthesis and release of positive
acute-phase proteins, including CRP. IL-6 is the major cytokine stimulus for
CRP production.
Serum amyloid protein (SAP)
UNDER THE INFLUENCE OF IL-6 THE LIVER PRODUCES A BUNCH OF ACUTE-PHASE PROTEINS

37. ACUTE-PHASE RESPONSE

38. RESOLUTION OF ACUTE INFLAMMATION

39. SEPTIC SHOCK Result: Triggering factors :
systemic infection (bacteraemia)
microbial cell wall products and/or
toxins released from the pathogens
Result:
Systemic activation of neutrophils and macrophages 
High level of cytokine (TNF-alpha) production: „cytokine storm”
Excessive inflammatory response

40. SEPTIC SHOCK The key molecule of the process: TNF-alpha
TNF-alpha and other inflammatory cytokines
multiorgan failure (MOF) is caused by the systemic vasodilation and hypoperfusion in shock and by multiple tromboses in DIC
DIC
capillar permeability blood pressure
high fever multiorgan failure
disseminated
intravascular
coagulation
Therapy: anti-TNF-alpha antibody

41. DIC Disseminated Intravascular Coagulation
pathologic activation of thrombotic process
distress of thrombotic process, bleeding
other causes:
snake bite, septic abortion, acute obstetric complications, malignant tumors, leukemias
Proinflammatory cytokines (IL-1, TNFα) and LPS/endotoxin leads to the release of Tissue Factor (TF) from cells which triggers the coagulation cascade.
The complement system also has an effect on blood clothing.

42. DIC: Disseminated Intravascular Coagulation