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Basic of immunology
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- 3. Basics of Immunology Whatis the immune system? • Biological mechanism for identifying and destroying pathogens within a larger organism. – Pathogens: agents that cause disease • Bacteria, viruses, fungi, worms, etc. • Types: • Innate Immunity • Adaptive Immunity 3
- 4. Immunity - Definition& Types 4 Adaptive Immunity Innate Immunity • Definition: • Resistance to infectious diseases and is mediated by immune system • Types: • Innate or Non Specific • Anatomic barriers: Skin, mucous membrane • Physiologic barriers: Temperature, pH • Phagocytic Barriers: • Inflammatory barriers: redness, swelling, heat and pain • Adaptive or Specific • Antigen specificity • Diversity • Immunological Memory • Self or non self recognition
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- 6. Adaptive Immunity -Types 6 • Naturally acquired Immunity Arises as a result of accidental interaction of a disease causing agent • Artificially acquired Immunity Immunity due to deliberate interaction of a disease causing agent. e.g.., vaccination The colors of the receptors indicate specificity: each can bind to one specific antigen. Adaptive immunity can only attack targets that it has prepared for
- 7. 7 Active Passive ActivePassive Antigens enter the body naturally; body induces antibodies and specialized lymphocytes Antigens are introduced by vaccination; body produces antibodies and specialized lymphocytes Antibodies pass from mother to fetus via placenta or to infant via the mother’s milk Preformed antibodies in immune serum are introduced by injection Adaptive Immunity Naturally acquired Artificially acquired Adaptive Immunity
- 8. Components of ImmuneSystem 8 • Cells • Antigen presenting cells • Polymorphic mono nuclear Leukocytes • Cytotoxic leukocytes • Natural Killer (NK) Cells • Lymphokine activated Killers (LAK) • Lymphocytes, B cells and T Cells • Proteins • Cytokines • Antibodies • Acute phase Reactants • Antibodies • Each B cell produces a specific type of antibody • Antigen: Antibody Generator • Any substance that can elicit an immune response when administered parenterally • Reacts with the antibody thus produced
- 9. Structure of Antibody •Composed of 2 heavy and 2 light chains – encoded by different genes • Single disulfide bond between heavy and light, two disulfide bonds between 2 heavy chains. • Light chain is either ƙ (kappa) or λ (lambda); 98% of mouse antibodies are ƙ. • Heavy chain constant region varies depending on isotype. 9
- 10. Epitope – ParatopeInteraction Variable and constant regions are encoded by different gene segments • variable region binds antigen • constant region binds receptors, bacterial products, complement, etc. 10
- 11. Types of Antibodies- IgG 11 • Induced by protein antigens • Constitutes about 80% of antibody in serum • Composed of two light chains (κ or λ) and one type of heavy chain (γ) • Coats Ag for its speedy uptake • Four isotypes • IgG1, IgG2, IgG3, IgG4 Most of BioGenex Antibodies are IgG Type
- 12. Types of Antibodies- IgA 12 • Constitutes 13% of total antibodies • Predominant class of Ab in extravascular secretions • Present in saliva, tears, nasal secretions, bronchial and digestive tract mucus and mammary gland secretions • Exists either as monomer or dimer • Dimer is formed by two IgA monomers, a J chain and secretory component • Has two isotypes IgA1 and IgA2
- 13. Types of Antibodies- IgM 13 • Largest antibody • Constitutes upto 8% of total Abs • It is a pentamer formed by five monomers of IgM Abs joined by disulphide bridges • First Ab that appears during immune response • Activates complement system
- 14. Types of Antibodies- IgD 14 • Membrane bound • Constitutes less than 1% of total Abs • Membrane bound and one of the main receptors on mature B cells • May play an important role in regulation of immune responses.
- 15. Types of Antibodies- IgE 15 • Constitutes less than 0.003% of total Abs • Triggers allergies • Binds to Mast cells and Basophils • Subsequent exposure to the same antigen triggers allergic reaction • Responsible for release of factors that attracts Eisonophils
- 16. Polyclonal vs. MonoclonalAntibodies 16 • Polyclonal Abs are produced from different clones of B cells for a given Ag • Recognizes the different epitopes on an Ag • Monoclonal Ab are produced against a single epitope
- 17. Polyclonal vs. MonoclonalAntibodies 17 • Polyclonal Abs is produced from different clones of B Lymphocytes and hence different antibodies with distinct specificity for given antigen (i.e same antigen different epitopes).It’s robust, exhibit cross reactivity • Monoclonal Abs is produced from a single clone and directed against a single epitope. It show lot to lot consistency and is specific
- 18. 18 Polyclonal vs. MonoclonalAntibodies Monoclonal Polyclonal Single plasma cell population / single epitope Multiple epitopes Higher Specificity Higher Sensitivity Hybridoma technology Produced in lab animals like Rabbit, Goat, etc. Lot to lot stability Lot to lot variations Longer time to generate Cross Reactivity
- 19. Applications of Antibodies •Western blotting: Detection of protein of interest in a mixture • Flow cytometry: Detection of proteins in live cells • ELISA: Binding characteristics of proteins and quantitation • IHC: localization of proteins of interest with in a cell • In situ Hybridization: detect modification and abnormalities at genetic level 19 Western IHC Direct Bind ELISA IP/ChIP Sandwich IF/Flow Cytometry Functional Modulation Denatyred/linear epitope folded/discontinuous epitope
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