CELL MARKERS IN HAIRY-CELL LEUKEMIA STUDIED IN CELLS FROM 51 PATIENTS

Abstract

To determine the maturation arrest of the neoplastic cells of hairy-cell leukemia (HCL) and the spectrum of the surface markers on these cells, a series of 51 patients with this disease was studied. The cells of all but 2 of the patients showed monoclonal surface Ig with respect to L chains. In .apprx. 1/3 of the cases, only .gamma. H chain determinants were present on the cells; the majority carried multiple H chain determinants as documented by the application of different fluorochromes. Two patients each showed 2 different clones of cells, both of the same L chain type. In 1 of these 2 patients, 2 paraproteins were present in the serum. Intracyto-plasmic Ig was found in only 4 of 39 cases, in all instances being IgM. All cases studied concerned cells with FcIgG receptors; however, the density of this receptor varied. FcIgM receptors also showed a spectrum of density, with some cases showing very few FcIgM-positive cells. Receptors for [complement] C3 were not observed on the hairy cells. Serum Ig levels were normal or increased. Paraproteins were found in the sera of 4 of 38 patients. These data suggest that HCL is a neoplasm of B lymphocytes. The neoplastic cells are probably arrested at a more mature stage than the cells of chronic lymphocytic leukemia. The multiple isotypes on the cells indicate a block at the switch phase from the small .mu.-carrying lymphocyte to the larger Ig-producing lymphocyte or plasma cell.