Chronic T cell lymphoproliferative disorder and pure red cell aplasia. Further characterization of cell-mediated inhibition of erythropoiesis and clinical response to cytotoxic chemotherapy

Two patients with pure red cell aplasia and a T cell lymphoproliferative disorder were studied in order to define the mechanism of suppression of erythropiesis and the patients' response to cytotoxic therapy. In vitro assays demonstrated enhanced formation of both erythroid colonies and bursts following T-cell depletion. Erythroid colony formation was suppressed by the readdition of autologous T cells to a null cell fraction of marrow mononuclear cells. Media conditioned by the patients' T cells did not exhibit any inhibitory effect on erythroid colony formation by autologous T cell-depleted marrow cells. These in vitro results suggested that T cell-mediated suppression of erythropoiesis was responsible for the generation of pure red cell aplasia. In both patients, cyclophosphamide therapy resulted in clinical remissions manifested by normalization of the hematocrits associated with a reduction in circulating lymphocytes from more than 10,000/mm³ to under 500/mm³. Maintenance chemotherapy has caused persistent inhibition of lymphocyte counts along with durable remissions with normal hematocrits.