Suppressive effect of rabbit anti-mouse brain serum (RAMBS) on murine pluripotent hemopoietic precursors in vitro and committed early erythrocytic and macrophage-granulocytic precursors detected after brief in vivo passage.

Antisera to mouse brain tissue have activity against mouse pluripotent hemopoietic stem cells (CFUS). In contrast to the suppressive effect of the antisera on in vivo colony formation of CFUs, it is known that in vitro colony formation from committed precursors, such as macrophage-granulocytic precursors (CFUC) and late erythrocytic precursors (CFUE) is not significantly suppressed. In the present experiments, the influence of rabbit anti-mouse brain serum (RAMBS) on colony formation from early erythrocytic precursors (BFUE) and pluripotent hemopoietic precursors in vitro (CFUMIX) was investigated. The number of colonies from both CFUMIX and BFUE did not decrease after preincubation with RAMBS and complement. However, when RAMBS-treated CFUMIX, BFUE, and CFUC were briefly exposed to an in vivo environment, all these precursors were almost completely removed, and also, CFUMIX, BFUE and CFUC seemed to share RAMBS reactivity.