Regulation of the development of plaque-forming cells to bromelain-treated syngeneic mouse erythrocytes in bone marrow cell cultures.

The development of plaque-forming cells (PFC) to bromelain-treated syngeneic mouse red blood cells (Br-MRBC) was studied in bone marrow cell (BMC) cultures. It was found that the number of marrow PFC to Br-MRBC does not show the typical spontaneous increase observed in spleen cell (SPC), or peritoneal cell (PC) cultures. The number of anti-Br-MRBC PFC was markedly increased by lipopolysaccharide (LPS), even in conditions in which cell proliferation was blocked by mitomycin C, suggesting the presence of high numbers of Br-MRBC-specific precursor cells, potentially capable of differentiating into autoantibody-producing cells, in the marrow. Moreover, the low levels of anti-Br-MRBC PFC were further reduced in the presence of concanavalin A (Con A). The addition of Con A-activated BMC to BMC, SPC, or PC cultures actively suppressed the development of anti-Br-MRBC PFC. Con A-activated BM suppressor cells were found to be Thy 1.2-negative, Ig-negative, nonadherent cells. A possible role for the BM suppressor cell in tolerance to self antigens is discussed.