idiotypic antibody

Anti-idiotypic antibody (anti-ID antibody) is a class of antibody that specifically binds to the antigen-binding site of an antibody. For each antibody molecule, the region that makes contact with an antigen is called complementary determining region (CDR) which is a unique site to be found within the variable (V) regions of an antibody heavy chain and light chain. The term idiotype refers to the whole collection of idiotopes contained in a single immunoglobulin molecule. Idiotopes may be either in the CDR or in the framework regions (FR) of the variable domain. Therefore, depending on the binding area within the immunoglobulin molecules, our anti-ID antibodies can be classified into four distinct types as follows: Type I anti-ID, of which the target idiotope is within CDR; Type II anti-ID, of which the target idiotope is within FR; Type III anti-ID, which may partially block Ag-Ab interaction; Type IV anti-ID, which recognize both idiotope of antibody and epitope of the antigen.