antiboy or immunoglobulin

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  • MUHAMMAD ASIF ZEBLECTURER HEMATOLOGYIPMSIMMUNOGLOBULIN

  • IMMUNOGLOBULINSIgs are glycoproteins, produced in response to an immunogen by plasma cells

  • STRUCTURE OF ANTIBODIESSimply Y shape structureComposed of 2 identical heavy polypeptide chains and 2 identical light chain.Heavy chain means have high molecular weight i.e 50,000-77,000d and composed of 450 amino acid.There are five chain classed of heavy chain i.e mu(u), gamma(r), alpha(a), delta(&) and epsilon(e)Light chain are smaller having molecular weight 25ooo and composed of 212 amino acidLight chain may be further divide into either kappa or lambda.Immunoglobulin may contain either kappa or lambda but not both

  • CONTILight and heavy chain are join to each other by disulfid bondThe light and heavy chain is composed of constant and variable region.The first 110-120 amino acid of the light and heavy region form variable sequence and thought to antigen binding site.The constant region is further divide into C1H,C2H and C3h each have their own function.In the medal of antibody a region called hinge region which gives feasibility to antibody.

  • IMMUNOGLOBULIN FRAGMENTS: STRUCTURE/FUNCTION RELATIONSHIPS

  • HUMAN IMMUNOGLOBULIN CLASSES Despite similarities, Abs are divided (size, charge, solubility) into distinct classes and subclassesIgG - Gamma () heavy chainsIgM - Mu () heavy chainsIgA - Alpha () heavy chainsIgD - Delta () heavy chainsIgE - Epsilon () heavy chains

  • IGGStructureMonomer

  • IGGStructurePropertiesMajor serum Ig about 85% of imunoglobulinMonomeric structureCan cross placenta as have receptor on placentaCan Fixes complement ( IgG4)Opsonin antibodies and help in phagocytosis.Incomplete antibodiesBest react at 37 c

  • IgG SubclassIgG1 - Gamma 1 (1) heavy chains have 2 inter chain disulfide bondIgG2 - Gamma 2 (2) heavy chains have 4IgG3 - Gamma 3 (3) heavy chains have 11IgG4 - Gamma 4 (4) heavy chains have 2

    Ig3 have highest ability to activate complement followed by Ig1 and then Ig2 while Ig4 cant

  • IGMStructurePentamer , so it can bind 10 antigen at a time.Extra domain (CH4)Also contain J chain which form disulfiod bond with hinge regionDiameter 300 AngstromLength of monomer is 100 A25-30 A width.

  • IGM

    Properties3rd highest serum Ig

    First Ig made by fetus and B cellsIt Fixes complementCan not cross placentaComplete antibodiesUsual temp 20c but best temperature is 4c

    Agglutinating antibody

  • Fixation of C1 by IgG and IgM AbsNo activationActivation

  • IGAStructureIn Serum 90% occurs as monomer and 10% as dimer.In Secretions (sIgA) 90% occurs as Dimer and 10% as monomer.SigA Have J chain in its structure

    Also have Secretory component.

  • IGAPropertiesIt is 2nd highest serum IgMajor secretory Ig (Mucosal or Local Immunity)Tears, saliva, gastric and pulmonary secretions and server as first lie of defense against microorganism invasion.Does not fix complementCannt cross placentaTemp 37cIgA subtypeIgA1 - Alpha 1 (1) heavy chainsIgA2 - Alpha 2 (2) heavy chains

  • IGDStructureMonomer

  • IGDStructureProperties4th highest serum IgB cell surface IgDoes not bind complementFunction is unknown but may important as lymphocytic differentiation.

  • IGEStructureMonomerExtra domain (CH4)

  • IGEStructurePropertiesLeast common serum IgBinds to basophils and mast cells (Does not require Ag binding)Allergic reactionsBinds to Fc receptor on eosinophilsDoes not fix complement

  • Abs: Molecules for immune effector system

    a. Activate C lysis & phagocytosis of microbes b. Binds to Ag enhance phagocytosis c. Recognition of target d. Stimulates degranulation of mast cells & release mediators e. Cross placental barrier

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