Class-switch recombination antibody

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... 

However, recent data obtained in humans also suggest direct actions of Tregs on B cells, as Lim et al. [31] have shown that isolated Tregs can suppress antibody production and the class switching recombination of B cells in the absence of T-helper cells. 

B.B., Crit. Rev. Immunol. 24, 297-320, 2004 Fiset, P.O., Cameron, L., and Hamid, Q., Local isotype switching to IgE in airway mucosa, J. Allergy Clin. Immunol. 116, 233-236, 2005 Min, I.M. and Seising, E., Antibody class switch recombination roles for switch seqences and mismatch repair proteins, Adv. Immunol. 87, 297-328, 2005 Apian, P.D., Causes of oncogenic chromosomal translocation. Trends Genet. 22, 46-55, 2006. 

Figure 6 Immunoglobulin heavy chain class switch recombination. (A) The murine heavy chain locus is shown before and after recombination from g. to yl, which results in expression of IgGl antibodies. Deleted sequences can be recovered in circular DNA molecules from B cells which have recently completed switch recombination. V, variable region C, constant region and S, switch region. (B) Examples of consensus G-rich repeats from some murine S regions...

Class switching When the complete heavy chain gene shown in Fig. 4 is transcribed, it generates a heavy chain for an IgM antibody since it is always the first C segment after the recombined VDJ (in this case CJ that is transcribed. To switch to making a heavy chain for a different antibody class, say IgA, the lymphocyte DNA has to undergo yet another recombination event that moves Ca next to... 

---