IMGT Education

Figure 1 - Schematic representation of an immunoglobulin

The variable domain of a light chain, or V-J-REGION, is encoded by two rearranged genes (one IGKV rearranged to one IGKJ for a kappa chain, one IGLV rearranged to one IGLJ for a lambda chain). The variable domain of a heavy chain, or V-D-J-REGION, is encoded by three rearranged genes (IGHV, IGHD, and IGHJ). The three hypervariable regions (or complementarity determining regions, CDRs) 1, 2 and 3 (hatched in the figure) determine the recognition and binding site to the antigen, in the three-dimensional structure. The constant region, or C-REGION, of the light chain is encoded by the IGKC gene (for the kappa chains), or one of the IGLC genes (for the lambda chains), and comprises a unique constant domain. The constant region of the heavy chain is encoded by one of the IGHC genes, and comprises 3-4 constant domains. CH1, CH2 and CH3 represent the constant domains of a heavy gamma chain. V=V-REGION, J=J-REGION, D=D-REGION (or more exactly N-AND-D-REGION to take into account the N-diversity), C=C-REGION. Intrachain disulfide bridge of each of the 12 domains are not shown. Interchain disulfide bridges correspond to those of an IgG1.

Click here for Spacefill 3D representation of an IgG immunoglobulin.