Non-specific suppressor cells in murine bone marrow chimeras: their possible role in GVHD-associated immunodeficiency

Suppressor cells against several mitogen-induced responses were detected in the spleen of murine bone marrow chimeras, regardless of intravenous (i.v.) or intrasplenic (i.s.) bone marrow transplantation (BMT). According to the time-course of the suppressor activity against Con A, PHA, and PWM, they were readily detected at 11-21 days after BMT and thereafter, either gradually decreased or remained at a plateau level. In contrast, the suppressor activity against the LPS-stimulated response increased at 39-52 days as compared to 24-34 days after BMT. Characterization studies of suppressor cells early (11-21 days) after BMT revealed that those in the i.v. and i.s. chimeras were composed of host-derived plastic dish adherent and/or anti-Thy 1.2 antibody-insensitive spleen cells in general. On the contrary, those in the i.v. and i.s. chimeras that possessed severer GVHD were mainly composed of host-derived plastic dish non-adherent spleen cells. Since the suppressor activity was higher in chimeras with severe graft-versus-host disease (GVHD) than in conventional chimeras, suppressor cells against the mitogen-induced responses may be related to the immunodeficiency associated with GVHD. Particularly, plastic dish non-adherent suppressor cells may closely relate to GVHD-associated immunodeficiency as compared with plastic dish adherent suppressor cells.