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NS, tens are small molecules which could, e, , immune response h, , Hap red by themselves, but when coupled with i h otc, , iniste ome immunogenic. Therefore, hapten is, , wae immune response); while hapten01 a, , (ell as antigen., , ding biologically important agents such as drugs, fat-soluble vitamins (e.g. Vit.-E),, , roids (lipids) and peptide hormones can func ions as haptens. These haptens in, s, , jugation with large proteins can be immunized to generate hapten-specific, Snes These antibodies can be used to detect the, oi i, , in the body., , Animal immunized with hapten-carrier conjugate can produce 3 types of antigenic, determinants: (i) anti-hapten antibodies, (ii) antibodies against carrier and (iii) antibodies, against new epitopes formed by conjugation of both“hapten and carrier., , Landsteiner used haptendinitrophenol (DNP) and carrier protein bovine serum, , abumin (BSA) and prepared the hapten-carrier conjugate i.e. DNP-BSA. When he, , inected/immunized the DNP-BSA conjugate to rabbit, he obtains three types of, antibodies., , , , , , , , , , , , , antigen but not an i, , carrier conjugate is both immunogen, , s, Role of haptens in diagnosis:, 1,, , , , In pregnancy test kit anti-hapten antibodies are used to detect the presence, of HCG in woman’s urine as a sign of pregnancy. , Antibody-based immunoassays are now routinely used to detect and monitor, the levels of specific chemicals in blood of patients. For example,, antileukotriene C4 (anti-lipid antibodies) is used to assay the level of

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v, IMMUNOLog,, , ma patients. Further, after successful] Bratt, drugs (¢.g., steroid like prednisone) jn bla, , leukotriene, , the levels of immuno-s, | can be maintained by i, , FACTORS INFLUENCING, , termine, , C4 in blood in asth, suppressive, immunoassays, IMMUNOGENICITY, , I nicity is de d by various properties of immunogen as wel] 7, mmunoge, the biological system. They are:, , A. Properties of the immunogen:, ¢ Molecular size, © Chemical composition and heterogeneity, , ° Foreignness, © Susceptibility to antigen processing and presentation with MHC molecule |, , B. Properties of the biological system:, , ¢ Host genetic makeup, * Dosage and rout of immunogen administration, , * Use of adjuvants to’ enhance immunogenicity, , >, , OG Molecular size: The molecular mass (size) of a macromolecule determines the, immunogenicity. Generally substances with a molecular mass less than 5000-10000, , Daltons (Da) are pore immunogens. The substances exceeding 10000 Da are most _, active immunogens., , G Chemical composition and heterogeneity: The chemical complexity of a molecule. |, affects immunogenicity. The synthetic homopolymers nonimmunogenic, irrespective, of their size. Therefore, immunogens are usually heteropolymers (composed of |, different ifferent types of aminoacids or sugars), which are influenced by moles |, , , , , , aight Penh Further, levels of organization - primary, secondary, tertiary and, quaternary- decides the structural complexity of a protein and thus contribute to, the immunogenicity., , Macromolecules that cannot be degraded and presented with MHC molecules are, poor immunogens, because the degradative enzymes within APCs can degrade, only proteins contain L-amino acids, polymers of D-amino acids cannot be |, processed. Large molecules are more readily phagocytosed and processed, $0, they are more immunogenic than smaller molecules., , Haptens like lipid antigens complexed with carrier proteins (e.g., BSA, OF KLH/, keyhole limpet hemocyanin protein) and immunized as lipid-protein conjugates, can induce B cells releasing specific antibodies against lipids., , G Foreignness: Host immune system can distinguish self from nonself and is usually, tolerant (nonresponsive) to self-antigens. In order to elicit an immune response, a molecule must be recognized as non-self (foreign). If a molecule has not bee?, , _—

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zt, , IMMUNOLOgy, , mc, , Adjuvants exert one or more of the following effects:, © Prolong the persistence of antigens. For example, in mice, Freund’s incomplete, , QQ, , adjuvant can prolong the persistence of antigen by slowly releasing the antigen, , from the site of injection., , Enhance immune responses. Adjuvants facilitate immune responses by, enhancing the expression of high levels of costimulators, MHC molecules on, APCs as well as the antigen presenting function of APCs. Adjuvants also, induce the release of cytokines. For example, Freund’s complete adjuvant, (powerful adjuvant than the incomplete adjuvant) when given in experimental, animals like mice, increase the phagocytic activity of dendritic. cells and, macrophages and induce higher expression of costimulators and production, , of cytokines that enhance T cell growth and differentiation., Adjuvants stimulate the non-specific proliferation of lymphocytes., Adjuvants stimulate local inflammatory response. Freund’s adjuvants and alum, can induce local inflammatory response leading to granuloma formation. These, adjuvants attract 6 guenigenear aon nel the site of injection., Sometimes a macrophage-rich dense mass develop called granuloma., Adjuvants induce enhanced primary T cell response to purified protein antigens, in vaccines by stimulating innate immune responses at the site of antigen, , exposure.