A monoclonal antibody that recognizes an Ly-6-linked antigen inhibits the generation of functionally active T cell subsets

A monoclonal antibody (mAb) generated against the chemically-induced BALB/c Meth A sarcoma, designated HD42, reacts in cytotoxic tests with Meth A as well as with BALB/c peripheral lymph node cells and mitogen-activated spleen cells. The antigen was detected by FACS analysis on BALB/c spleen and lymph node cells, and by absorption assays on all normal lymphoid cells of BALB/c but not B6 mice. The expression of the antigen was not found on normal adult lung fibroblasts, on brain, nor on an extensive panel of tumors of BALB/c and B6 origin. Because the strain distribution of the antigen is reciprocal to that of Ly-6.2 and is not expressed in congenic C3H.Ly-6b mice, we have tentatively defined it as Ly-6.1 and referred to the mAb as alpha-Ly-6.1. The presence of alpha-Ly-6.1 abrogates both the Con A-induced and the IL 2-dependent proliferative response of normal T cells, whereas the response of normal B cells to LPS remains unaffected. alpha-Ly-6.1 is a potent suppressor of the primary in vitro plaque-forming cell (PFC) response to SRBC. Pretreatment of normal splenic T cells with alpha-Ly-6.1 and complement had no effect on the ability of these cells to generate in vitro either T helper cells (TH) or T suppressor cells (TS) to SRBC. However, addition of antibody in the absence of complement during the generation of TH or TS, or posttreatment of these T cell subsets with antibody and complement after in vitro education, completely removed the functional activity of these cell types. Addition of alpha-Ly-6.1 to MLC suppressed the MLR as well as the generation of cytotoxic lymphocytes (CTL), whereas the presence of the antibody during a cell-mediated lympholysis (CML) had no effect. Therefore, it appears that alpha-Ly-6.1 recognizes an antigen that is important for the generation of TH and TS cell subsets.