Studies of the mouse Ly-6 alloantigen system

Three monoclonal antibodies were produced by fusing mouse myeloma cell line NS-1 with spleen cells from C3H/An mice hyperimmunized with B6-H-2^k spleen cells. These antibodies recognized an alloantigen displaying a similar strain distribution pattern to the Ly-6.2 and Ala-1.2 alloantigens. Analysis of C×B and B×H recombinant inbred mice revealed close linkage of genes controlling Ly-m6 and Ly-6. The monoclonal antibodies lysed 70 percent of cells in lymph nodes and 60 percent in spleen in direct cytotoxicity assays, but did not lyse significant numbers of cells of thymus and bone marrow. Separated T and B cells were reactive with the antibodies, but T cells were more sensitive to the antibody and complement than B cells. Virtually all cells in cultures of cells activated in the mixed lymphocyte reaction or by Concanavalin A were reactive with the monoclonal antibodies. Direct plaque-forming cells were completely eliminated by the monoclonal antibody and complement. By absorption tests, cells from all organs tested so far (thymus, lymph node, spleen, bone marrow, brain, kidney and liver) were shown to express the Ly-m6 determinant. Tumor cell lines with T, B or stem cell characteristics were reactive with the monoclonal antibody by direct cytotoxicity and absorption assays.