Immune pancytopenia.

Circulating T-lymphocytes from a 13-year-old boy with autoimmune anaemia, severe neutropenia and thrombocytopenia inhibited autologous and normal homologous bone marrow myeloid colony formation in vitro. This inhibition was abolished when the patient's antithymocyte globulin and complement-treated T-lymphocytes were used. T-lymphocytes from normal individuals did not cause such an inhibition. The patient's lymphocytes showed no inhibitory effect on erythroid colony formation. Investigation of the patient's serum failed to disclose any leucoagglutinin, lymphocytotoxin or humoral factor against myeloid colony formation. These findings indicate that T-lymphocytes may play a role in the pathogenesis of neutropenia in immune pancytopenia.