Haemopoietic stimulators and inhibitors in aplastic anaemia serum

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Abstract
Normal serum and serum from 4 patients with severe aplastic anemia was fractionated by Sephadex G-150 gel filtration. Fractions were tested for direct hemopoietic activity on colony forming cells in methylcellulose cultures, and for their indirect influence on hemopoiesis via CSA[colony stimulating activity]- and BPA[burst-promoting activity]-producing cells. All aplastic anemia sera contained abnormal inhibitors and stimulators. An inhibitor acting on both hemopoietic and factor producing cells, eluting with the IgM fraction was found in all, variable inhibitors of lower MW in single patients. Stimulatory activity of 10,000-50,000 MW acting on factor producing cells, but not on colony forming cells directly, was found in all, a variable stimulator eluting with the very high MW fraction in single patients. In 2 patients who achieved complete autologous bone marrow remission after treatment with high dose immunosuppression. Sephadex fractions of serum before treatment and remission serum were simultaneously tested on autologous bone marrow in remission. Inhibitors were detected before treatment and disappeared in remission, stimulators were not detectable before treatment but became strong in remission. The effect of aplastic anemia serum on hemopoiesis in culture apparently is determined by the balance of inhibitors and stimulators on both hemopoietic and CSA/BPA producing cells.