Antigen & antibody
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This presentation provides an overview of antigens, antibodies, and immunoglobulins. It discusses the structure and types of antibodies, including IgG, IgA, IgM, IgD, and IgE. The properties and functions of immunoglobulins are also summarized. Key points covered include the Y-shaped structure of antibodies, the roles of antibodies in agglutination, precipitation, and activation of the immune response, and the use of antibodies and immunoglobulins to identify and respond to foreign antigens in the body.
Antigen & antibody
- 1. Presentation on ANTIGEN AND ANTIBODY 1
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- 3. oINTRODUCTION oHISTORY oSTRUCTURE OF ANTIBODY oTYPES OF ANTIBODY oIMMUNOGLOBULINE AS ANTIGEN oPROPERTIES OF IMMUNOGLOBULINE oPROPERTIES OF ANTIBODY oFUNCTION OF IMMUNOGLOBULINE oCONCLUSION oREFRENSH 3
- 4. ANTIGEN A substance that can produce a specific immune response when it is introduced into The tissue of an animals and that can react specifically with antibodies or sensitised Cells is known as an antigen. the ability of an antigen to produce an immune response and to react with the Product an is known as antigenicity. The ability of a material to induce an immune Response is referred to as immunogenicity and such materials are known as immuno- Gens. EPITOPES AND PARATOPES The part of the antigen with which the antibody reacts is known as the epitope or Antigenic determinant . The portion of the antibody molecule that binds to the epitope Is called the paratope. The epitope determinant is bound to the specific antibody by Non-covalent bounds and their binding is more or less three dimensional and may 4Be similar to a lock and key fit
- 5. 2.CHEMICAL NATURE:- Most of the naturally occurring antigens are proteins and Polysaccharides and these antigens are found to be compa- Ratively more antigenic than lipids and nucleic acids. Proteins are better antigenic when compared to polysacha- Rides of the same size. 3.SOLUBILITY:- The nonantigenicity of synthetic polymers also attributed to their insolubility in body fluids and any substance which is not con- Verted to soluble forms by tissue enzymes are also not antigenic For example pneumococcal polysaccharides are greater immuno- Genic for mice than for rabbits because of the greater hydrolytic Activity of mouse liver enzymes for these polysaccharides. 5 SOME ESSENTIAL FACTORS FOR ANTIGENICITY 1.SIZE:- The molecular size of an antigen has a direct relation to antigenicity Very large molecules such as hemocyanin (6,000 mol.wt.) thyroglobulin(669 mol.wt.) and tetanus toxin(55,000 mol. Wt.) are excellent antigens .
- 6. 4.FOREIGNNESS:- To be antigenic the macromolecule must come from a foreign Source . Antigens from related species are less antigenic than of Unrelated species and antigens from members of same species Are less antigenic than that of other species. For example plant Proteins are good antigens in animals whereas duck serum Proteins are not good antigens for chick. CROSS REACTIVE ANTIGENS:- Antigen antibody reaction is specific and th Specificity is determined by spatial configuration of the specificity is determined by Spatial configuration of the antigenic determinant group .but the antigen specificity Is not absolute . Cross reactions can occur between antigens which bear stereochemic Similarities. Cross reacting antigen is one which is capable of binding to antibody Produced in response to a different antigen. 6
- 7. INTRODUCTION:-- 1.Immunoglobulin are immunologically active serum proteins formed in response to a antigen and react specifically with that antigen. 2. A blood protein produced in response to and counteracting a specific antigen. 3. Antibodies combine chemically with substance which the body recognizes as alien, such as bacteria , viruses, and foreign substances in the blood. 4. Antibody are Y-shaped proteins which play a pivotal role in our immunity against bacterial and viral infection. 7
- 8. HISTORY:- •Rodney porter (1962) :-proposed the basic structure of immunoglobulin. Immunoglobulin is glycoprotein. •Georeges kohler and cesar milstein (1975):- signally the start of the modern of antibody research and discovery. • Gerald edelman(1959):- indenpendently published the molecular structure of antibody .for which they were later joinyly awarded the nobel prize. 8
- 10. TYPES OF ANTIBODY :-- 1.(IMMUNOGLOBULINE A ) IgA 2.(IMMUNOGLOBULINE D ) IgD 3.(IMMUNOGLOBULINE E ) IgE 4.(IMMUNOGLOBULINE G ) IgG 5.(IMMUNOGLOBULINE M ) IgM 10
- 11. 1.(IMMUNOGLOBULIN G ) IgG :-- IgG is immunoglobulinG. It is an antibody It is a glycoprotein it is Y shaped. It is a relatively stable four polypeptide chained Molecule formed of 2 light chains(kappa or lemda ) and 2 heavy chains of (gamma) .There are 4 antigenicity distinct subclasses of igG namely igG1 , igG2, igG3 , igG4. The molecular weight of IgG is 150,000 and its sedimentation is 7s. 11
- 12. 2.( IMMUNOGLOBULINE A ) IgA:-- IgA is an antibody. IgA is found in serum. IgA is glycoprotein . It is Y- shaped. It is a two types , namely serum IgA and secretory IgA , Secretory IgA is seen in the external seromucous secretion of the respiratory, gastro intestinal and urinogenital tracts . The IgA is synthesised by plasma cells in the lamina propria of mucous membran and intracellularly by the secretory cmponent and J-chain. 12
- 13. 3.(IMMUNOGLOBULIN M ) IgM:-- IgM is an antibody. It is the largest of the immunoglobulins . It is the often referred as the macroglobulin because of its high molecular weight (950,000). It is Y Shaped. They are polymers of usually 5 molecules (pentamers) each with polypeptide chains. A monomeric form (7s) of IgM is found on the B lymphocytes. The serum level of IgM is very low, about 5 to 2 mg/ml. 13
- 14. 4.(IMMUNOGLOBULIN D ) IgD :-- IgD has a typical immunoglobulin structure with two light chain kappa or lamda type. The two heavy chain are of delta type. IgG is slightly larger than IgG, having a molecular weight of 180,000. IgD is limited to the blood serum .The average serum level is 0.03 mg/ml. It is found associated with the surface of B-lymphocytes. 14
- 15. 5.(IMMUNOGLOBULIN E ) IgE:- 1.Immunoglobulin E is a monomer having a typical immunoglobulin structure. It has 2 light chains and 2 having chains. The light chain is kappa or lemda type. The heavy chain is of epsilon. The very low level of IgE is only because it is synthesised by a very few plasma cells in the body . It ‘s carbohydrate content is about 12%. 15
- 17. Isotypic Determinants -These determinants distinguish the C regions of the H chain classes (and subclasses) and the L chain types. Each isotype is encoded by a distinct gene that is characteristic for a particular mammalian species and is present in all members of that species. Antibodies to these determinants may be raised by injecting IgG from one species into another species. Each Ig class (IgG. IgM, IgA, IgD, and IgE) possesses a specific isotypic determinant on its H chain. Allotypic Determinants -The second group of antigenic determinants are those found on the Igs of some, but not all, members of a particular species. Allotypic determinants reflect genetic polymorphism of Igs within one species. Antibodies can be formed against an allotypic determinant by injecting Igs into another member of the species that does not possess the alloantigen. In human the Gm antigens are a good exam Idiotypic Determinants -The third group of antigenic determinants of Igs exist as a result of unique structures generated by the hypervariable subregions (or complementarity- determinging regions CDR) on L and H chains. The antigenic determinants are called idiotopes, analogous to epitopes of classical antigens. Alpha-idiotopes lie outside the Ag-binding site. Beta-idiotopes are close to the antigen binding site. Gamma-idiotopes are formed by the antigen binding site. 17
- 18. PROPERTIES OF IMMUNOGLOBULINS:-- 1.) Immunoglob0ulins are glycoproteins. 2.) They have a shape of Y and T. 3.) The molecular weight ranges from 150000 to 950000. 4.) Typically an immunoglobulin molecule is made up of four polypeptide chains of which 2 are light chains and the remaining 2 are heavy chains. 5.) They cross placenta (IgG). 6.) They have reaginic activity (IgE) 7.) They are involved in complement fixation (IgG & IgM). 8.) They fix macrophages (IgG). 9.) They fix mast and basophil cells(IgE). 10.) They agglutinant antigens. 18
- 19. FUNCTIONS OF IMMUNOGLOBULINS:- The main function of the immunoglobulin is protection of the body against. the Invading micro-organism. The protective role is carried out in the following ways: 1. Agglutination of antigens . 2. Precipitation of antigens . 3. Lysis of the antigens . 4. opsonisation . 5. Tissue fixation. 6. Phagocytosis. 7. Chemotaxis. 8. Activation of mast cells and basophils. 19
- 20. CONCLUSION:- When an immunoglobin reacts with an antigen,it is called an antibody. When it does not react with an antigen it is simply called immunoglobins. All antibodies are immunoglobins; but all immunoglobins may not be antibodies. REFRENCE:-- K.C. SONY 20
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