In vitro investigation of autoantibody-secreting peritoneal cells and their regulation.

A high proportion of peritoneal cells from untreated mice, after 4--5 days in culture, develop into plaque-forming cells against bromelain-treated mouse red blood cells. The number of plaque-forming cells was increased significantly by exposing the peritoneal cells to ammonium chloride to lyse red blood cells before culture. Conversely, the increase was significantly inhibited by adding before culture untreated or bromelain-treated sheep or mouse red blood cells. Treated or untreated horse or rat red blood cells did not inhibit the increase. Treating peritoneal cells or subpopulations of peritoneal cells with anti-theta serum and complement before culture caused a significant increase in the number of plaque-forming cells against bromelain-treated red blood cells after 3--4 days of culture. Various procedures were used to fractionate peritoneal cells into B-cell enriched and B-cell depleted subpopulations before culture and after culture, to investigate whether some of the plaque-forming cells could be attributed to phagocytic cells. Generally, changes in the number of plaque-forming cells against bromelain-treated mouse red blood cells paralleled changes in B-cells. In some experiments the proportion of plaque-forming cells observed represented up to 85% of the B-cells present. The results suggest that the high level of autoreactivity is due to antibody production by B-cells and that phagocytic cells are not forming spurious plaques. Further, it appears that the autoimmunity is regulated by T-cells and can also be inhibited by mouse RBC.