IMMUNOREGULATORY ROLE OF BONE-MARROW .2. CHARACTERIZATION OF A SUPPRESSOR CELL INHIBITING THE INVITRO ANTIBODY-RESPONSE

The addition of bone marrow cells (BMC) to spleen cell cultures suppressed the antibody response in a dose-dependent manner. This suppression required viable cells. Treatment of BMC with anti-thymocyte serum did not affect the suppressive activity and BMC, but not spleen cells, from nude mice inhibited the antibody response to the same degree as marrow from normal littermates. BMC which had been depleted of macrophages with antimacrophage serum or carbonyl iron showed increased suppressor activity. Furthermore, fractionation of BMC by velocity sedimentation and resetting revealed the suppressor cell to be a medium-to-large Fc receptor-positive lymphocyte. Absence of detectable B or T cell markers on the suppressor cell indicates this cell to be an Fc-positive null lymphocyte, possibly a precursor cell, which inhibits the response of mature lymphocytes. © 1979.