Modification of exogenous haemopoietic spleen colony formation in irradiated mice by antisera against mouse thymocytes and mouse brain.

Treatment of donor bone marrow in vitro with both anti-thymocyte serum (ATS) and anti-mouse brain serum (RAMBS) inhibits the formation of haemopoietic spleen colonies in irradiated and reconstituted mice. This activity of the antisera may be completely (ATS) or partly (RAMBS) eliminated by absorption with thymocytes. The effect of the antisera is complement-independent. Most likely it depends on the existence and functionality of phagocytes (macrophages) in the recipients.