Rearrangement of a chicken immunoglobulin gene occurs in the lymphoid lineage of transgenic mice.

Immunoglobulin (Ig) and T-cell antigen receptor genes rearrange through identical heptamer-nonamer recognition sequences during entry of cells into the B or T lymphoid lineage. A similar enzymatic machinery may be used to perform these highly cell-specific events in these two types of lymphoid cells. We have investigated what the signal may be that triggers the rearrangement of one or other of the receptor genes in B or T cells. Mice from three transgenic lines carrying two, four or twenty copies of the unrearranged chicken lambda light-chain locus were analysed. In all three lines the chicken Ig transgene rearranges in B cells; in the line with 20 copies, a rearranged fragment can also be detected in thymus DNA. We conclude that the inserted chicken light-chain locus in its natural configuration contains target sequences that permit specific rearrangement in mouse lymphoid B cells, but that this precise differentiation step may be deregulated in thymic cells when the physiological level of relevant information is experimentally altered.