The frequency of multiple recombination events occurring at the human Ig kappa L chain locus.

Products of Ig kappa L chain gene rearrangement in a variety of human B cell samples were investigated by sequential Southern blot hybridization analysis. By application of four region-specific probes (C kappa, J kappa, U' kappa and kappa de) a complete spectrum of kappa rearrangements, including both predicted and novel products, were detected. Nearly 30% of the products detected reflect multiple recombination of the kappa locus. The kappa-deleting element was responsible for 70% of the multiple rearrangements that were detected. Interestingly, eight kappa-expressing samples exhibited rearrangement of the kappa-deleting element. The remaining multiple recombination products were characteristic of double V kappa-J kappa rearrangement. This frequency reveals that secondary V-J rearrangement may significantly contribute to the expression of kappa L chains in humans.