PCR analyses of the κL chain locus in single B-lineage cells of wild- type, Cκ-, or JCκ-deficient homozygous or heterozygous mice often detect multiple in- and out-of-frame rearrangements at the λL and λL loci. They are most frequent in small pre-BII cells and equally so in wild-type and κL chain-deficient cells. Hence, κL chain production appears not to inhibit secondary rearrangements. Around 20% of all small preBII cells express IgL chains in their cytoplasm. Cells with a first productive rearrangement on one allele are favored to enter the immature B cell compartment. Thus, allelic exclusion might be secured by control of accessibility of IgL chain loci for rearrangement and by rapid selection of cells with a fitting over those with a nonfitting IgL chain.
Yamagami, T., Ten Boekel, E., Andersson, J., Rolink, A., & Melchers, F. (1999). Frequencies of multiple IgL chain gene rearrangements in single normal or κL chain-deficient B lineage cells. Immunity, 11(3), 317–327. https://doi.org/10.1016/S1074-7613(00)80107-7