Haematopoietic suppressing activity of gamma-interferon in serum and bone marrow of aplastic anaemia patients.

To determine the mechanism by which haematopoiesis is suppressed in aplastic anaemia, the effect of the sera from 6 patients on the granulopoietic precursors (colony-forming units in culture; CFU-C) was studied in vitro. Addition of the sera from 2 patients significantly suppressed CFU-C. The suppressive effect of the sera on CFU-C was inhibited by the addition of 1.5 NU/ml of anti-gamma-IFN antibody. In another patient, anti-gamma-IFN antibody increased autologous CFU-C although the serum of the patient did not suppress CFU-C. Serum gamma-IFN levels of all patients were under 2 IU/ml. The above findings suggest that humoral factors inhibit haematopoiesis in some patients with aplastic anaemia, and that gamma-IFN plays a role as an inhibitor even at a low concentration.