The murine kappa light chain shift

Abstract

THE immunoglobulins of mice and other animals consist of several distinct heavy chains associated with either of two light chains (κ or λ). Adult animals of different species produce immunoglobulins which demonstrate widely divergent ratios of κ to λ light chains. In mice, most of B-cell surface immunoglobulins possess κ light chains¹. However, as all previous work on the ratio of κ/λ immunoglobulins was based on experiments with adult animals, the possibility that immature populations of B cells may demonstrate a more evenly balanced ratio of κ to λ positive cells was investigated. In this study, populations of cells known to contain immature B lymphocytes were examined by indirect immunofluorescence for the presence of κ and λ positive cells. The results demonstrate that fetal liver, bone marrow and spleens from young mice contain B cell populations with a κ/λ ratio approaching unity. In the spleen, the κ/λ ratio increased as a function of age with the most dramatic shift occurring between 4 and 6 weeks of age. A similar, but less dramatic increase in the κ/λ ratio occurs in the bone marrow. Based on these data, we propose that the final predominance of κ-bearing cells is based on a two-stage process. Initially, there is an equal probability of κ or lambda; light chain expression at the cell surface. However, the κ-bearing cells, which possess a more abundant repertoire of V_κ genes, eventually predominate as a result of antigen driven clonal expansion.