Heavy chain diversity generation

Gough, N.M. Bernard, O. (1981). Sequences of the joining region genes for immunoglobulin heavy chains and their role in generation of antibody diversity. Proc. Natl. Acad. Sci. USA 78,509-513. 

Fig. 1. The arrangement of germline genes in mice (from Tonegawa, 1983). The exact number of variable heavy genes is not known, but is somewhere between 200 and 1000. This results in between 12,000 and 60,000 different possible heavy chains, leading to possible library sizes on the order of 107-108 (data are for mice and are taken from Seidman and Leder, 1978a Seidman et al. 1978b). Somatic mutation and junctional diversity further augment the size of this theoretical library to sizes that far exceed the number of B cells in a mouse (Rajewsky, 1996). For example, if any ten residues are mutated to any of the other nineteen amino acids, library size is increased by a factor of 1910. Thus, diversity in the immune system is not limited by diversity-generating mechanisms.

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