antibody structure and function

The gene loci responsible for coding the heavy chain or light chain includes the gene region for variable domains and constant domains. The variable domain gene region is constituted by variable (V), diversity (D) and joining (J) segments for heavy chain, and only V and J segments for light chain gene. V, D or J segments comprises multiple copies of tandemly arranged V, D or J genes flanked by conserved Recombination Signal Sequences (RSS) which can be recognized by V(D)J recombinase and subsequently processed by other recombinational factors to randomly delete spare V, D and J genes. By this manner, randomly selected one V, one D and one J (only V and J for light chain) genes are linked together to form the variable gene region for transcription. Given that human has 44 V gene copies, 27 D gene copies and 6 J gene copies, antibodies pool with imaginable diversity can be produced. This process is called V(D)J recombination.