Idiotype

In immunology, an idiotype is a shared characteristic between a group of immunoglobulin or T cell receptor (TCR) molecules based upon the antigen binding specificity and therefore structure of their variable region. The word idiotype comes from two Greek roots, idio meaning 'private, distinctive, peculiar' and typos meaning 'mark.' Thus idiotype describes the distinctive sequence and region that makes any immunoglobulin/TCR unique from others of the same type which is its variable region. The variable region of antigen receptors of T cells (TCRs) and B cells (immunoglobulins) contain complementarity determining regions (CDRs) with unique amino acid sequences. They define the surface and properties of the variable region, determining the antigen specificity and therefore the idiotope of the molecule. Immunoglobulins or TCRs with a shared idiotope are the same idiotype. Antibody idiotype is determined by