Regulation of kappa/lambda immunoglobulin light chain expression in normal murine lymphocytes

Past work has demonstrated that the kappa:lambda ratio in serum immunoglobulins varies significantly among species. In murine systems it has been established that serum levels of immunoglobulins containing kappa and lambda light chains are present in concentrations of 95 and 5%, respectively. The experiments reported here were designed to determine the molecular basis for this unbalanced ratio. We examined spleens and Peyer's patches (PP) of CBA/J mice for the ratio of kappa to lambda for surface Ig expression, mRNA accumulation, transcription and in vitro translation. Studies of the levels of B-cells expressing kappa and lambda revealed the percentages to be similar to the protein concns in serum (90% kappa +, 10% lambda +). However, further analysis of light chain mRNA accumulation and nuclear transcription revealed ratios of kappa:lambda only slightly greater than 1.0 in most cases. In addition, in vitro translation of B-cell-derived mRNA demonstrated greater translation of kappa chains relative to lambda, though clearly not totally sufficient to provide a serum ratio of 95:5. The results suggest that the low concn of serum lambda relative to kappa in the mouse is most likely due to post-translational events such as inefficient protein processing, poor association with heavy chains, etc. In addition, these data support the hypothesis that lambda-mRNA is present in some kappa-bearing B-cells since lambda-mRNA levels are higher than one would predict from a population of cells in which only 5% express surface lambda chain protein.