SOMATIC DIVERSIFICATION OF THE CHICKEN IMMUNOGLOBULIN LIGHT CHAIN GENE IS LIMITED TO THE REARRANGED VARIABLE GENE SEGMENT

Previous studies have shown that the chicken .lambda. immunoglobulin light chain gene undergoes a single rearrangement that results in functional VJ joining of the unique variable (V.lambda.1) and joining (J.lambda.) coding regions. The immunologic repertoire of .lambda. genes is created through extensive sequence diversification within the rearranged locus during B cell development in the bursa of Fabricius. This sequence diversification was detected only at the rearranged V.lambda.1 segment and not within the 5'' leader sequence, the J.lambda. segment, or the unrearranged V.lambda.1 segment. The selective diversification of the rearrangedd V.lambda.1 segment was associated with unique DNAase I-hypersensitive sites on the rearranged allele. While probes for V.lambda.1 sequences detect multiple homologous V.lambda. segments, probes for both the 5'' leader and j.lambda. segments fail to detect homologous sequences. Taken together, these results suggest that a highly selective process, possibly gene conversion, operates during B cell ontogeny to generate diversity within the .lambda. gene.