Novel recombinations of the Ig κ-locus that result in allelic exclusion

Allelic exclusion of Ig H and L chain gene loci serves to ensure that a B cell expresses a single specificity antibody. The analysis of Abelson murine leukemia virus transformed cells that rearrange the κ-locus during growth in cell culture has provided the opportunity to characterize intermediate steps in Ig gene rearrangement. By sequential cloning of an Abelson murine leukemia virus transformed cell line we have observed a novel two-step pathway that results in a rearrangement of a Vκ gene segment into the J-Cκ intron. This type of rearrangement effectively excludes functional κ expression from that allele. A truncated mRNA product resulting from the Vκ signal exon splicing to the Cκ exon is diagnostic of these unique rearrangements. In addition to demonstrating a novel mechanism for allelic exclusion, the two-step pathway described serves to explain how V-intron recombination products were generated in previously described cell lines.