Acquired aplastic anemia in adults. IV. Histological and CFU studies in transplanted and non-transplanted patients.

A follow-up study of 10 patients suffering from acquired aplastic anaemia, comprising methocrylate-embedded bone marrow biopsies and CFU cultures, is presented. The haematopoietic recovery patterns and changes in the inflammatory infiltration after permanent engraftment could be distinguished from those in non-transplanted patients. After anti-thymocyte globulin treatment followed by allogeneic bone marrow infusion, the recovery pattern resembled that in non-transplanted patients. The persistently low colony-forming capacity in some patients could be explained by the existence of lymphoid inhibitory cells, which suggests an immunologic auto-destructive mechanism.