Antibodies somatic recombination

Antibodies have been studied most extensively in the mouse, an ideal vertebrate for both genetic and biochemical manipulations. It is believed that mice can synthesize more than a million antibodies with different antigenic specificities. This enormous diversity of proteins is generated from a limited amount of genetic information with the help of two mechanisms Somatic recombination and somatic mutation. 

No complete antibody gene exists in germ-line cells. The genes for light chains and heavy chains assemble by somatic recombination during B-lymphocyte maturation. 

Fig. 1. In the germ-line (embryo) DNA, sequences coding for the variable (V) region lie distant from those encoding the constant (C) region. During the differentiation of B lymphocytes, these two sequences are brought together to form an active antibody gene by deletion of the intervening DNA (somatic recombination).

Describe the contributions of the number of immunoglobulin genes (the germ-line repertoire), somatic recombination, and somatic mutation in the generation of antibody diversity. Describe the roles of the V, C, D, and J segment genes in these processes. 

As compared to DCs, B cells are very poor APCs and play a major role as source for antibodies. Upon stimulation by antigens and in the presence of T cells at the border of the T-cell-B-cell area, adjacent to follicles, B cells become antibody-secreting cells and eventually form a germinal center (GC) response. GCs are specialized follicles for B-cell expansion, somatic hypermutation, and class switch recombination, processes that are regulated by T cells, follicular DCs, and other cells. In this process of B-cell maturation, Tregs seem to play a critical role, as in several immune diseases, which are characterized by aberrant antibody... 

---