Studies on the pathogenesis of refractory anemia.

Nine patients with refractory anemia were studied using the soft agar marrow culture assay (CFU-c) to identify granulocyte-monocyte progenitor cells. Patients' marrows were then cocultured with normal marrow to identify suppressor cells that inhibit normal colony formation. Three of nine patients had low colony formation and no suppression in coculture. These patients may have a defect intrinsic to the marrow granulocyte-monocyte progenitor cell, termed type I. Three of nine patients had normal colony formation and no suppression in coculture, possibly representing a type II defect in the hemopoietic environment. Three of nine patients had low colony formation in the CFU-c assay and their marrow contained cells that suppressed colony formation by normal marrow in coculture. This defect, termed type III, may result from suppressor cells. Thus, refractory anemia may be a syndrome resulting from at least three different pathogenetic mechanisms involving defects in (1) stem cells, (2) the marrow environment or (3) suppressor cells. This may represent one end of the spectrum of pancytopenia with diminished cellularity (aplastic anemia) or normal cellularity (refractory anemia) resulting from similar mechanisms.