Regulation of DNA synthesis and antibody production by soluble factors released by bone marrow cells

Bone marrow cells (BMC) suppressed the antibody response of spleen cells across a cell impermeable membrane. Fractionation of BMC supernatants by column chromatography and ultrafiltration revealed the presence of a suppressor factor and an enhancing factor which acted antagonistically. Bone marrow enhancing factor (B-EF) had a molecular weight greater than 20,000, enhanced antibody synthesis, and stimulated DNA synthesis in thymocytes but not BMC. Bone marrow suppressor factor (B-SF) was produced by non-adherent BMC, had a molecular weight 1000 to 10,000, suppressed the antibody response in vivo and in vitro, and stimulated DNA synthesis in BMC but not thymocytes. The possible role of these factors in homeostasis and regulation is discussed.