Re-evaluation of the probabilities for productive rearrangements on the κ and λ loci

Abstract

V-J rearrangements at Ig light chain (IgL) genes occur in resting small pre-B cells. In the absence of cell division, the probability of productive K and h rearrangements is proportional to the output of κ+ B and λ+ B cells in bone marrow. The kinetics and probability of productive κ or λ rearrangements was assessed in three groups of mice carrying two (wild-type), one or no intact Igκ gene, and the following conclusion are drawn. κ and λ rearrangements occur independently at different kinetics, and rearrangements are initiated at a time when κ rearrangements are stopping. The probability of productive κ and λ rearrangements per chromosome is calculated to be ~60 and ~20% respectively. Thus, a κ gene can attempt rearrangements up to three times per chromosome during B cell development. These findings explain that the observed ratio of κ+ B/λ+ B cell production in wild-type mice is 95/5.