The feasibility of using antigenically disguised skin xenotransplants to cover extensive burns for a suitable time lag without administering immunosuppressive drugs was tested experimentally. Pieces of human skin that had been preincubated for 3 h at 37 degrees C with either mouse anti-human beta 2-microglobulin monoclonal antibody (beta 2m-McAb) or PBS (controls) were grafted onto the backs of immunologically competent Swiss mice, and the time required for their rejection or substitution by normal autogenous skin was determined. Thus, it was found that the beta 2m-McAb-pretreated xenografts had a significantly longer mean survival time than the control grafts. An even longer skin xenograft MST was obtained when beta 2m-McAb was repeatedly injected, at weekly intervals, just beneath the transplants. Parallel immunohistochemical studies showed that the beta 2m-McAb entered the grafts and was bound to its targets both in epidermis and dermis. Moreover, a small amount of beta 2m-McAb administered at the outset significantly hindered the reactive proliferation of primed mouse spleen cells cultured in the presence of human epidermal cells. Finally, neither toxic effects nor a weakening of immune competence were elicited by repeated intraperitoneal injections of beta 2m-McAb. Therefore, it seems expedient to propose the use of beta 2m-McAb to delay the rejection of skin xenografts as this antibody harmlessly prevents, wholly or in part, the activation of the recipients' lymphocytes. This would positively aid any patient urgently needing xenograft cover of extensive burns.