Cutting edge: recombinase-activating gene expression and V(D)J recombination in CD4+CD3low mature T lymphocytes.

The recombinase-activating genes, RAG-1 and RAG-2, can be expressed by a subset of B cells within germinal centers, where they mediate secondary V(D)J rearrangements. This receptor revision mechanism could serve either receptor diversification or tolerance-induced functions. Alternatively, it might rescue those cells the receptors of which have been damaged by somatic mutation. Less is known about the occurrence of similar mechanisms in T cells. Here we show that mature T cells with defective TCR surface expression can express RAG genes and are capable of initiating secondary V(D)J rearrangements. The possibility that a cell rescue mechanism based on the generation of a novel Ag receptor might be active in peripheral T cells is envisaged.