A trial of immunotherapy in aplastic anemia and pure red cell aplasia.

Immunotherapy, consisting of lymphocyte depletion or plasmapheresis in combination with cyclophosphamide and prednisone, was employed in three patients with refractory pure red cell aplasia and six patients with aplastic anemia of various etiologies. All three patients with pure red cell aplasia responded to plasmapheresis. One patient with atypical aplastic anemia showed partial recovery following lymphocyte depletion; the other five patients showed no evidence of a clinical response. The effect of patients' sera or bone marrow on formation of myeloid or erythroid colonies by bone marrow from normal individuals was determined in vitro. A decline in serum inhibition of erythroid colony formation was observed in the patients with pure red cell aplasia following treatment. Any changes in serum inhibition were less marked or unrelated to treatment outcome in the patients with aplastic anemia, although the single patient who responded to lymphocyte depletion exhibited reversal of coculture bone marrow inhibition. Our experience suggests that in vitro assay methods may not adequately predict the response of patients with aplastic anemia to this form of immunotherapy, and furthermore clinical improvement was too sporadic for this treatment to be recommended. Plasmapheresis may be a useful adjunct in patients with pure red cell aplasia, but remissions may not be dramatic or sustained.