Ly-4.2: a cell membrane alloantigen of murine B lymphocytes. III. In vitro studies

The alloantigenic specificity Ly-4.2 is present on a restricted population of murine lymphocytes which have previously been shown to have some of the properties generally ascribed to B lymphocytes, both with regard to distribution and function. In the study reported herein, the effect of anti-Ly-4.2 and anti-Thy-1.2 (θ) antisera have been examined in various in vitro systems. (a) T cell-mediated lysis of ⁵¹Cr-labeled P815-X2 target cells by immune allogeneic peritoneal exudate cells is inhibited by anti-Thy-1.2, but not affected by the anti-B (Ly-4.2) reagent. (b) Antibody-dependent lymphocyte-mediated lysis of ⁵¹Cr-labeled sheep red cells was only slightly inhibited by anti-Ly-4.2 and anti-Ig antisera, and not at all by anti-Thy-1.2 antisera, indicating that this type of cell lysis is mediated by neither T (Thy-l⁺) nor B (Ly-4.2⁺,Ig⁺) cells. (c) The response of lymph node lymphocytes to various mitogens was affected thus: PHA, completely inhibited by anti-Thy-1.2 but not by anti-Ly-4.2; Con A, largely inhibited by anti-Thy-1.2, and slightly by anti-Ly-4.2; PWM (pokeweed mitogen), partially inhibited by both antisera; E. coli endotoxin lipopolysaccharide, greatly inhibited by anti-Ly-4.2 but only slightly by anti-Thy-1.2. The findings demonstrate that anti-Thy-1.2 reacts predominantly with T cells and anti-Ly-4.2 with B cells.