antibody structure

Antibody, Y shaped protein complex belonging to immunoglobulin (Ig) superfamily, exists in many kinds of organisms, especially higher animals. Specific antibody can bind specifically to particular exogenous pathogen like virus or bacteria to either directly neutralize the pathogens by blocking its active sites or facilitate the elimination of pathogens by other immune cells, such as macrophages. Antibody is produced by B lymphocytes (plasma cells). B cells initially express antibodies on the cell membrane as B cell receptors (BCR). When BCRs are coupled with desired pathogens, B cells are differentiated into plasma cells, producing a myriad of antibodies. Part of plasma cells transform into memory cells which respond relatively fast to the same substance upon later infection.