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AT8-1-12-5, an intracytoplasmic gamma 2b-producing (mu- gamma 2b+) pre-B cell line transformed with Abelson murine leukemia virus continuously generated intracytoplasmic mu, gamma 2b-producing (mu+ gamma 2b+) cells during propagation in culture. Southern blotting, DNA cloning and sequence analysis showed that these mu+ gamma 2b+ cells were generated from the mu- gamma 2b+ pre-B cells by VH replacement events. The gene segments involved in these replacement events were restricted to only two VH gene segments, VH7.1 (VH7183 family) and VH6.2 (VHQ52 family). Cell staining using the monoclonal anti-VH141 antibody 3-5-6f that specifically recognized the VH6.2 but not VH7.1 gene products indicated that half of the VH replacement events occurring in AT8-1-12-5 used the VH6.2 gene segment. Deletion mapping indicated that the incoming VH gene segments, VH7.1 and VH6.2 were proximal to the resident VH gene segment, VH12.5 (VH7183 family). These results provided direct evidence of the biased usage of VH gene segments in VH replacement and have several implications for the mechanisms of VH replacement.

AT11-2, an Abelson virus-transformed cell line has DJH complexes on both chromosomes and is able to form functional variable region genes by the joins of VH genes to the DJH complexes during culture. Therefore we examined which VH gene family was used in functional VH to DJH recombinations in AT11-2. Surprisingly, of 32 independent functional VH to DJH recombinational events in AT11-2, 31 events used the VH segments of the VHQ52 family, and the remaining one used the VH segment of the VH7183 family. Thus, we describe here the first B precursor cell line that almost selectively uses the VHQ52 family in functional VH to DJH rearrangements. The selective use of the VHQ52 family in this B precursor cell line strongly indicates nonrandom use of VH gene families, and the existence of a stage at which the VHQ52 family is preferentially used during the normal development of early pre-B cells and has important implications for understanding the ontogeny of VH repertoire development. Furthermore, this cell line should prove extremely valuable in further studies of this kind.