Immunologic and functional features of the leukemic cell of hairy cell leukemia: evidence for a Null hypothesis

We report results of the immunologic evaluation of three unusual patients with hairy cell leukemia (HCL) whose HC were surface immunoglobulin (slg) negative. Mononuclear cell preparations containing 82%, 51%, and 42% hairy cells (HC), respectively, were obtained from three males with the typical syndrome and characteristic tartrate-resistant acid phosphatase-staining HC. Monocyte features were lacking in that HC did not stain for alpha-napthylacetate esterase, lacked receptors for C3, failed to produce chemiluminescence, and produced decreased 51Cr release in antibody-dependent cellular cytotoxicity against human red cell targets. Receptors for sheep erythrocytes, a T-cell marker, were decreased. Evidence against a B-cell origin of HC was provided by low numbers of slg staining and C3 receptor-bearing cells. Our results favor the hypothesis that HC in these three patients represent neoplastic proliferation of Null lymphocytes. Such an origin may explain the heterogeneity of markers previously described on HC of patients with HCL.