Coculture studies of 16 untransfused patients with aplastic anemia.

We studied the effects of peripheral blood lymphocytes from 16 untransfused patients with severe aplastic anemia (AA) of diverse etiologies on the growth of granulocyte-macrophage colonies from normal marrows. Normal lymphocytes in our system increased the number of granulocytic colonies by 31 +/- 6% (mean +/- SEM). Lymphocytes from 3 of 16 untransfused AA patients significantly inhibited growth in HLA-matched sibling marrows (-30%, -40%, and -37%; p less than 0.01). Although these results suggest that the majority of cases of AA are not mediated by a coculture-detectable immunologic mechanism, studies using lymphocytes obtained from AA patients before transfusions may detect the subpopulation whose disease is immune-mediated and who may therefore respond to immunosuppressive therapy.