Serum inhibitors in aplastic anaemia.

To study the frequency and clinical importance of serum factors inhibiting CFU-c in patients with aplastic anaemia, sera from 21 patients were analysed. The sera of eight patients showed inhibition of at least one normal bone marrow, but strong and consistent inhibition of two or more normal bone-marrow samples was found in only two cases. In both of these two patients the inhibition disappeared after successful therapy. Fair, but not complete, correlation was found between serum inhibitors and HLA-antibodies, suggesting that at least part of these inhibitors are antibodies directed against HLA-antigens present on myeloid progenitor cells. Serum inhibitors appear to be infrequent in the population of patients with aplastic anaemia seen in our hospital and appear to have no major implications for therapy or outcome of the disease.