Heterogeneity of Pathogenetic Mechanisms in Aplastic Anemia

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Abstract
The mechanisms responsible for the bone marrow failure in 21 aplastic anemia patients were studied by the colony-forming units in culture assay (CFU-C). Twelve patients had no detectable in vitro defect that could be responsible for the low CFU-C numbers. Three patients had suppressor T cells that inhibited CFU-C (P < 0.001); 1 of 2 patients responded to antithymocyte globulin therapy and the 3rd recovered spontaneously. Three patients had serum inhibitory immunoglobulins directed against their marrow CFU-C; plasmapheresis caused recovery of bone marrow function. Three patients had abnormalities at the colony-stimulating factor level: 2 had inhibitors of colony-stimulating factor, corrected in vitro and in vivo by indomethacin and cholinergic agonists (P < 0.01); and the 3rd had colony-stimulating factor generation defect, corrected in vitro and in vivo by Li. Testing for cellular or humoral suppressor factors directed against precursor cells or for abnormalities at the colony-stimulating factor level gives helpful guidelines to therapy in aplastic anemia.