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IMMUNOGLOBULINS CHEMISTRY& FUNCTIONS.ppt
- 2. immunology isoe of the rapidly advancing ranch of medicine 3 salient features of immunological reaction are Recognition of self from non self or forigei substances Specificity of reactions Memory of the respose
- 3. The Immune Response Immunity:“Free from burden”. The resistance exhibited by the host towards injury caused by microorganisms and their products. Immune Response: Involves production of antibodies and generation of specialized lymphocytes against specific antigens. Antigen: Molecules from a pathogen or foreign organism that provoke a specific immune response.
- 5. Any sustance thatinvokes an immuogical respone is an antigen or immunogen Microbes: Capsules, cell walls, toxins, viral capsids, flagella, etc. Nonmicrobes: Pollen, egg white , red blood cell surface molecules Lipids and nucleic acids are only antigenic when combined with proteins or polysaccharides. Antigens
- 6. HAPTEN: Small foreignmolecule that is not antigenic. Unable to induce Ab formation on its own Must be coupled to a carrier molecule to be antigenic. Eg: Steroids, DNP- dinitrophenol group.
- 7. EPITOPE: Small partof an antigen that interacts with an antibody. Any given antigen may have several epitopes. Each epitope is recognized by a different antibody.
- 9. Immunoglobulins arefreely circulating proteins. Antibodies are those Immunoglobulins possess a demonstrable specificity for a given antigen. Each antibody has at least two identical sites that bind antigen: Antigen binding sites. Antibodies
- 10. ANTIGENS- Anysubstance which provokes an immunological response. (eg- microbes/ pathogens) Epitope: Small part of an antigen that interacts with an antibody ANTIBODIES- Bodies response to antigens . (eg- immunoglobulin) PHAGOCYTOSIS- foreign substances are ingested and digested intracellularly. 10
- 12. 3 majorcomponents of the odys immune system are lymphocytes( cells)- derived from one marrow T lymphocytes (T cells)-orginate from thymus Innate immune system cells are responsile for the synthesis of circulating ,humoral antiodies - immunogloulins
- 13. Immunoglobulins constitutea heterogeneous group of serum proteins which function as antibodies. 20% of total serum proteins Glycoproteins-(82-96% polypeptide & 4-18 % of carbohydrate) Polypeptide part contribute for all the biological functions of Igs
- 14. Consist of4 polypeptide chains 2 heavy (H and 2 light L chains 4 chains are linked y disulfide Bonds Pairs of heavy and light chain combined to form y shaped molecule
- 16. A flexibleY-shaped molecule with four polypeptide chains: 2 identical light chains 2 identical heavy chains Held together by interchain disulfide bridges
- 17. Each polypeptidechain is made up of a no.of loops or domains of constant size(100-110 AA residues) formed by intrachain disulfide bonds. L &H chains subdivided into variable & constant region Variable Regions: N-terminal domain of each chain shows more variation in aminoacid sequence than the others Contain the antigen binding sites L chain consist of 1 variable and 1 constant region
- 18. Constant Regions:Stem of monomer and lower parts of Y arms. Aminoacid sequence constant in this region L chain consist of 1 variable and 1 constant region -VL , CL H chains – 1 variable &3 constant regions VH,CH1,CH2,CH3
- 19. Hinge region:the zone where variable & constant regions join. Flexible region between CH1 and CH2 – allows better fit with antigen surface Variable regions of both the light and heavy chains form antigen binding site Constant region of heavy chain responsible for various biologic functions like complement activation
- 20. Constant regionof light chain has no known function Variable regions of both h and L chains have 3 extremely variable amino acid sequences at the amino terminal end called hypervariable region Specificity of antibodies is due to these hypervariable regions
- 22. Enzyme papinsplits immunoglobulin molecule in the hinge region into two fragments named as Fab & Fc Fc region: Constant part & does not take part in antigen binding associated with secondary biological activities of Igs Eg: complement fixation Fab – variable part ,site of antigen binding
- 24. Molecular wt.approx. 23000 Two types Kappa (K) & Lambda(λ) on the basis of structural differences in the constant regions Ig always contains identical K or λ chains In human Kchain are more freqeunt than λ in Ig molecule
- 25. The heavychains are structurally & antigenicly distinct in different classes of Igs. Five classes of H chains have been identified Gamma (γ) , Alpha (α) , Mu (μ), Epsilon (ε) and Delta (δ) . Molecular wt vary from 50,000 to 70,000 The classes of H chains determines the classes of immunoglobulins
- 26. IgG- Gamma(γ) IgA - Alpha (α) IgM- Mu (μ) IgE - Epsilon (ε) IgD- Delta (δ) .
- 27. Structure: Monomer(2 heavy& 2 light) Heavy chains are gamma type Percentage serum antibodies: 75- 80% Distributed in intra-vascular & extra vascular compartments Half-life in serum: 23 days IgG-
- 28. Principal Antibodyof secondary immune response Defense against bacteria & virus Crosses Placenta &protect newborns from infections These maternal antibodies are seen in neonatal circulation upto 2-4 months Rh immunization
- 29. Opsonizes bacteria, making them easier to phagocytose neutralizes bacterial toxins and viruses, Fixes complement which increases bacterial killing protects fetus and newborn.
- 30. Structure: Occursin two forms Serum IgA – monomer Secretory IgA – Dimer Dimeric molecule formed by 2 monomer units connected at their carboxy terminal by a protein termed J chain They also have a secreatory component attached to the dimer
- 31. Secreatory pieceis produced in liver, reaches intestinal mucosal cells ,combines with IgA dimer to form secreatory IgA Secratory component provides passage to the mucosal surface and also protects from being degraded in the intestinal tract Second major serum Ig (10-13%) Found in external secreations such as colostrum,saliva,tears,respir atory,intestinal secreations Prevent attachment of bcteia virus to mucous surface Also found in internal secreations such as synovial,amniotic,pleural – serum type IgA
- 33. Structure: PentamerHAVING 5 IDENTICAL IMMUNOGLOBULIN MOLECULE JOINED TOGHER BY J CHAIN macroglobulins Percentage serum antibodies: 5-8% Location: Blood, lymph, B cell surface IT HAS 10 ANTIGEN BINDING SITE MOST EFFICIENT Ig in agglutination,complement activation Predominant antibodies in primary response . II. IgM
- 34. Provide defenseagainst bacteria and virus Natural antibodies Eg: A blood group Ag persons have anti- B Ab in blood
- 35. IV. IgD Structure:Monomer Percentage serum antibodies: 0.2% Location: B-cell surface, blood, and lymph Half-life in serum: 3 days Known Functions: In serum function is unknown. On B cell surface, initiate immune response.
- 36. V. IgE Structure:Monomer Percentage serum antibodies: 0.002% Location: Bound to mast cells and basophils throughout body. Half-life in serum: 2-3 days Mediate allergy, hypersensitivity & anaphylaxis Defends against worms. High level in asthma, hay fever, parasitic infections
- 38. 1.multiple myeloma Plasma cell cancer due to abnormally high concentration of serum immunoglobulins usually IgA & IgG LIGHT CHAINS ARE PRODUCED IN EXCESS THAN HEAVY CHAIN they enter bloodstream, because they have low molecular weight- pass throuh glomerular membrane & appear in urine These protein chains of low molecular weight are known as BJP
- 39. Portions ofheavy chain deleted during synthesis Cannot join with L chains of normal Ig Defective H chains excreated through urine Gamma chain disease associated with hepatosple nomegaly &lymphadenopathy Alphain chain disease seen in abdominal lymphoma,malabsorption
- 40. Waldenstrom’s Macroglobulinemia IgM level in blood is increased considerably with a monoclonal peak. This is due to malignant proliferation of IgM clones. Since IgM are macromolecules, they may form aggregates or cryoprecipitates, serum viscosity is increased.
- 41. HYPOGAMMAGLOBULINEMIA: Underproduction ofIgs Agammaglobulinemia: total absence of Igs X linked Highly susceptible to infections HYPOGAMMAGLOBULINEMIA: Seen in chronic lymphatic leukemia Nephrotic syndrom