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Antigens, Immunogens , Epitopes, and Haptens

Antigens, Immunogens , Epitopes, and Haptens. Innate and adaptive immunity:. 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.

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Antigens, Immunogens , Epitopes, and Haptens

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  1. Antigens, Immunogens , Epitopes, and Haptens

  2. Innate and adaptive immunity:

  3. Innate (Natural) Immunity: • Inborn resistance. • present the firsttime 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 • A variety of proteins and enzymes (present in human blood and tissue fluids) are considered the first part of innate immunity. • 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: • IFN-α produced by dendritic cells • 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 andtissues. - 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. Cytokines: IL1, IL6, IL12 & TNFα. Interferons: IFα and IFβ. Complement Cytokines: IL2, IL3, IL10 & IL13. Interferons: IFγ Immunoglobulins. • n Phagocytes: monocytes, MQ & DC Granular leukocytes T lymphocyte & B lymphocytes 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-HistonsAntibodies will be produced.

  16. Immunogenicity and Properties of immunogen: • Immunogenicity is the ability of immunogen to activate immune response. • Properties of Immunogen: • Foreignness • Size • 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. • Homopolymersare 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. • Immunodominantepitope 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 cytokines.

  23. n

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

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

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

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