Abstract

The sera of 28 patients with aplastic anaemia were examined for their effect on granulocyte colony growth in soft agar. Normal sera did not affect colony growth, but 13 sera from patients with aplastic anaemia, three from multiparous women, and six from patients polytransfused for various disorders caused colony inhibition. This inhibition was not due to the presence of HLA antibodies in aplasia patients because some sera inhibited HLA compatible bone marrow, and polyspecific HLA antibodies were not found in all inhibitory sera. All patients who failed to show engraftment or who rejected their bone marrow graft within three weeks had serum inhibitory to normal bone marrow cell culture, but inhibition could not be demonstrated against autologous bone marrow cells in these patients with aplastic anaemia. The results show that patients with serum inhibitors have an increased risk of early graft rejection and suggest that this rejection is mediated by antibodies directed against bone marrow stem cells.