The Monoclonal Antibodies αS-HCL 1 (αLeu-14) and αS-HCL 3 (αLeu-M5) Allow the Diagnosis of Hairy Cell Leukemia

To define cell surface antigens associated with hairy cell leukemia (HCL), and to gain better insight into the origin of this disease, we developed monoclonal antibodies against spleen cells of a patient with this disease. Although none of these antibodies alone proved specific for the leukemic cells, two of them, designated αS-HCL 1 (aLeu-14) and αS-HCL 3 (αLeu-M5) were found to be valuable in the diagnosis of HCL when used in combination. αS-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 molecular weight of 150,000 daltons (150 kilodaltons). αS-HCL 1 expression on hairy cells is markedly increased when compared with normal B lymphocytes isolated from peripheral blood, tonsils, and spleens. αS-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 (