CFU-GM inhibitors in neutropenia.

Peripheral blood lymphocytes from 20 patients with neutropenia not consistent with aplastic anaemia were tested for their ability to inhibit the proliferation of normal granulopoietic precursor cells (CFU-GM) in agar culture. Two patients, both with features of an autoimmune disorder, had lymphocytes which were more inhibitory than normal lymphocytes to both normal and their own CFU-GM. Two other patients had lymphocytes which were more inhibitory than normal lymphocytes to either their own CFU-GM or normal CFU-GM but not both. Eight patients had lymphocytes which were significantly less inhibitory than normal lymphocytes to either normal or their own CFU-GM, but only one showed this feature against both normal and their own CFU-GM. One patient had a highly potent plasma inhibitor of CFU-GM--this patient had received multiple transfusions and had a leucocyte antibody of a broad specificity. No clinical or haematological features were common to any of these groups of patients which reflects the heterogeneity of patients studied and stresses the importance of controls.