The 3' enhancer region determines the B/T specificity and pro-B/pre-B specificity of immunoglobulin V(sub kappa)-J(sub kappa) joining

The immunoglobulin kappa gene 3' enhancer (E3') suppresses V(sub kappa)-J(sub kappa) recombination and restricts it to the pre-B developmental stage of B cells. The B/T specificity of V(sub kappa)-J(sub kappa) recombination is controled by the PU.1 binding domain in E3'. A mutation in the PU.1 domain causes recombination in both B and T cells. Deletion of E3' causes rearrangement of the kappa gene in the early pro-B stage of B cells.