Studies on non-H-2-linked lymphocyte-activating determinants: IV. Ontogeny of the MlS product on murine B Cells

Abstract

The minor lymphocyte stimulating (Mls) locus codes for lymphocyte activating determinants (LADs) on murine B lymphocytes, but not T lymphocytes. This observation was strengthened by a series of techniques which allow deletion and addition of T and B cells. These included the use of cytotoxic antisera such as anti-Thy 1.2, anti-MTLA, anti-MBLA, and complement, and the use of a goat anti-μ antisera, and finally the use of a fluorescence activated cell sorter (FACS). The studies in this report document the organ distribution and the ontogenetic appearance of the surface LADs on the surface of B lymphocytes from DBA/2N (H-2 d, Mls a) and CBA/J (H-2 k, Mls d) mice. Adult-like ability to stimulate H-2 identical BALB/c (H-2 d, Mls b) and C3H/He (H-2 k, Mls c) responder cells appeared at about 4–5 weeks of age. Inability of neonatal cells to induce an Mls-defined MLC was found not to be due to a low frequency of B lymphocytes or to the presence of suppressor cells, but due to the absence of the Mls-coded LADs on their surface. These data support the concept that the Mls-coded LADs are present on adult B lymphocytes and are specific markers of B-cell differentiation, which is preceded by membrane IgM and the δ homologue of human IgD, Ia, and the receptor for the third component of complement.