immunoglobulin - PDF document

I I m m m m u u n n i i t t y y D D r r . . O O s s a a m m a a A A b b o o E E l l N N a a s s r r 0 0 1 1 2 2 5 5 0 0 2 2 4 4 7 7 4 4 5 5 Structure of immunoglobulin s ( antibodies) M.W: (90.000 – 150,000) Structure: ( Y - shaped ) immunoglobulin molecule consists of 2 iden tical light chains (L) disulp hide bonds 2 identical heavy chains (H) Each heavy & light chain has Variable portion Constant portion Has a different A.A. sequence for each antibody. (FC) is responsible for complement activation , It is the site of antigen binding diffusion of the antibodies in the tissues Fab (fragment for antigen binding) & adherence of antibodies to specific structure Types of antibodies ( G A M E D ) Immunoglobulin G Immunoglobulin M Immunoglobulin A Immunoglobulin D Immunoglobulin E Properties Monomer , low M.W. The highest conc . (80%) Penta mer Monomer , di m mer or trimmer Monomer Monomer Functions  Complement activation.  Has a ntiviral, antibacterial & antitoxic activities  Responsible for the 2ry response.  Responsible for the passive immunity in the fetus from mother  Rh antibodies are of the IgG type (can cross the placenta)  Complement activation .  Responsible for the 1ry response .  ABO antibodies are of the Ig M type (cannot cross the p lacenta)  The main antibody in secretions (as tears, saliva, breast milk….)  Plays an important role in 1 st line defense at mucosal level against viral infections.  Responsible for antigen recognition by B - cells.  Important in parasitic infectio ns & some allergic responses.  Degranulation of mast cells by IgE coated antigens.