Antibodies

• Antibodies are Y shaped proteins secreted by plasma B cells in response to one type of foreign antigen
• Antibodies are made from 4 polypeptide chains, 2 heavy and 2 light
• The variable region is where the antibody binds to an antigen
• The constant region stays the same for all antibodies
• Variable ends house the 2 antigen binding sites which are complementary to the foreign antigen
• The chains are connected together with disulphide bridges
• Agglutination is when antibodies clump foreign antigens together
• Agglutination makes it easier for phagocytes to engulf, digest and destroy the pathogen
• ELISA stands for enzyme-linked immunosorbent assay
• In ELISA, an antigen is attached to the well
• If there was no antigen present, the enzymes would not be bound by any antibodies so they will not react with the substrate
• A sample which may contain the antibodies is added to the well
• The well is washed, then a second antibody with an enzyme attached is added
• The well is washed again, then a solution is added which changes colour if the enzyme is present
• Monoclonal antibodies = antibodies produced by a single clone of B cells
• Polyclonal antibodies = antibodies produced by many different B cells