1. Antigens, Immunogens, Epitopes, and Haptens

2. Innate and adaptive immunity:

3. Innate (Natural) Immunity:  Inborn resistance.  present the first time a pathogen is encountered (does not require prior exposure)  Usually not specific  not modified by repeated exposure to the pathogen.

4. Adaptive (Acquired) Immunity:  weak or absent at the first exposure.  specific  increases dramatically with subsequent exposures to the same pathogen (Memory)

5. Types of innate immunity:  Humoral (soluble)immunity  Cell mediated immunity Types of adaptive immunity  Humoral (soluble)immunity  Cell mediated immunity

6. Soluble mediators of innate immunity: Proteins and enzymes Cytokines & type 1 interferons. Complement

7. Proteins and enzymes o A variety of proteins and enzymes (present in human blood and tissue fluids) are considered the first part of innate immunity. o Example: C reactive protein (CRP), lysozymes, and defensins.

8. n Cytokines, and Type I interferons: Cytokines: IL-1, IL-6, IL-12, and TNFα produced by activated phagocytes. Type I interferons: o IFN- α produced by dendritic cells o IFN-β Produced by fibroblasts. -INFs are rapidly produced, within minutes by the infected cells (virus infection).

9. Cells of Innate immunity: Phagocytes: - Monocytes and macrophages: blood stream and tissues. - Dendritic cells: lung, and GIT mucosa. Granular leukocytes: -Neutrophils, and eosinophils. -Basophils and mast cells. Natural killer cells (NK).

10. Adaptive Immunity: Soluble mediators of adaptive immunity: - Cytokines: IL-2, IL-3, IL-10,IL-13. - Interferons: INF-γ (Gamma). - Complement. Soluble and cell-bounded proteins: -The Immunoglobulins. Immune cells: - T lymphocytes - B lymphocytes - N.K cells.

11. n Phagocytes: monocytes, MQ & DC Granular leukocytes Cytokines: IL1, IL6, IL12 & TNFα. Interferons: IFα and IFβ. T lymphocyte & B lymphocytes Cytokines: IL2, IL3, IL10 & IL13. Interferons: IFγ Immunoglobulins. Complement NK cell

12. n

13. Antigens, Immunogens, Epitopes, and Haptens

14. Antigen: Is a molecule or part of a molecule that is recognized by the immune system. Immunogen: Is an antigen that evokes a specific, positive immune response.

15. Example: Injecting a laboratory animal by human chromosome Anti-DNA antibodies and anti-Histons Antibodies will be produced.

16. Immunogenicity and Properties of immunogen:  Immunogenicity is the ability of immunogen to activate immune response.  Properties of Immunogen: o Foreignness o Size o chemical nature and complexity.

17. Foreignness: Immune system can discriminate between foreign and self substance (self & non self) Size: Molecular weight of at least 10,000 Dalton. Chemical nature: -Mainly proteins (polypeptide) -Carbohydrates, steroids, and lipids are poor immunogens.

18. n Chemical complexity:  As the chemical complexity increases; the immunogenicity increases.  Homopolymers are poor immunogens regardless of size, while heteropolymers are strong immunogens.  Proteins are heteropolymers (different amino acids)

19. n Epitopes (The Antigenic determinants):  The smallest part of an antigen or immunogen that can be recognized by the B & T cells receptors. So it is the basic recognition element.  A single antigen molecule may have several different epitopes.  Immunodominant epitope is an epitope that can stimulate a greater antibody response than others.

20. N epitopes

21. B cell receptors can recognize epitopes whether they are:  free soluble molecules.  Surface-bound molecules.  Degraded fragments. T cell receptors can bind only to epitopes which are surface-bound molecules.

22. Superantigen : is a substance such as a bacterial toxin that is capable of stimulating multiple T lymphocytes, leading to release of relatively large quantities of cytokine s.

24. n

25. Hapten: Small, non-biologic molecules that bind to immune cells receptors but cannot by themselves induce a specific immune response.

26. (Land-Steiner’s experiment). Injected a mice with: hapten No immune response carrier (protein) Anti carrier Hapten + Carrier Anti-Hapten + Anti-Carrier

27. T-cell dependent and T-cell independent Antigens: Antigens are classified as either T-cell dependent or T-cell independent. T cell dependent antigen activates immune system depending on T- lymphocytes.

28. T-cell dependent antigen T-cell independent Antigen Structural properties ComplexSimple Chemical natureProteins, glycoprotein, and lipoproteins Polysaccharide; bacterial Lipopolysaccharide. Antibody - class induced IgG, IgM, IgA, IgD, and IgE Only IgM Immunological Memory yesNo Present in most Pathogens yesNo