Removal of T cells from bone marrow for transplantation. Comparison of rat monoclonal anti-lymphocyte antibodies of different isotypes.

We describe a family of six rat monoclonal antibodies which appear to recognize identical or closely related determinants present on virtually all mature human lymphocytes and monocytes, but absent from other blood cells including myeloid and erythroid colony-forming cells. Four IgM antibodies and one IgG2a fix human complement; one IgG2c antibody does so only poorly. All of the antibodies react with lymphocytes from baboons, rhesus and cynomolgus monkeys. However, in all baboons and rhesus monkeys tested, and some cynomolgus monkeys, they also recognize red cells. Nevertheless, in other cynomolgus monkeys reactivity is with lymphocytes only, so these animals will be suitable models for testing the effects of the antibodies in vivo. The antibodies described here could be useful for in vitro removal of lymphocytes from allogeneic marrow grafts (to prevent graft-versus-host disease) or malignant lymphoid cells from autologous grafts (for treatment of leukaemia) and may also find application as general immunosuppressants and for immunotherapy of leukaemia.