THE MONOCLONAL-ANTIBODIES ALPHA-S-HCL 1 (ALPHA-LEU-14) AND ALPHA-S-HCL 3 (ALPHA-LEU-M5) ALLOW THE DIAGNOSIS OF HAIRY-CELL LEUKEMIA

Abstract

To define cell surface antigens associated with hairy cell leukemia (HCL), and to gain better insight into the origin of this disease, monoclonal antibodies were developed against spleen cells of a patient with this disease. Although none of these antibodies alone proved specific for the leukemic cells, 2 of them, designated .alpha.S-HCL 1 (.alpha.Leu-14) and .alpha.S-HCL 3 (.alpha.Leu-M5) were found to be valuable in the diagnosis of HCL when used in combination. .alpha.S-HCL 1 recognizes an antigen associated with > 95% of B cells in the peripheral blood. Biochemical analysis identified this antigen as a single polypeptide chain with a MW of 150,000 daltons (150 kilodaltons). .alpha.S-HCL 1 expression on hairy cells is markedly increased when compared with normal B lymphocytes isolated from peripheral blood, tonsils and spleens. .alpha.S-HCL 3 reacts with an antigen present on hairy cells but also on monocytes, macrophages, in a lower density on neutrophils, and a small percentage (< 2%) of lymphocytes. The antigen recognized by .alpha.S-HCL 3 is composed of a non-covalently linked biomolecular complex of 90 and 150 kilodaltons. Since the HCL 3 antigen was not detectable on other lymphomas of either T or B cell type, the co-expression of S-HCL 1 and S-HCL 3 on hairy cells is a unique marker for this disease.