GP-70, a novel B-cell mid-stage differentiation antigen associated with B-type leukemias and lymphomas: Current Status

GP-70 is a newly described B-cell associated surface membrane glycoprotein of 70 000 dalton molecular weight. GP-70 is sensitive to various proteases, but not to neuraminidase, and the carbohydrate moiety is linked to the protein moiety via an N-glycosidic linkage. Monoclonal and polyclonal antibodies were generated and used to determine the distribution of GP-70 relative to another B cell marker-surface membrane immunoglobulin (SmIg) in a variety of cell lines and in B-cell neoplasias. Of all the cultured cells tested only Burkitt's lymphoma cell lines were positive for GP-70. Peripheral blood mononuclear cells derived from 93 patients with chronic lymphocytic leukemia (CLL), 11 with non-Hodgkin's lymphoma (NHL), 5 with Burkitt's lymphoma and leukemia (BL) and 4 with hairy cell leukemia (HCL) were studied. In addition, 179 samples obtained from healthy individuals (PBL), 21 cases of acute non-lymphoblastic (ANLL) and 29 cases of common type-acute lymphoblastic leukemia (CALL) were also examined. GP-70 was present in all cases of HCL, BL and NHL in leukemic phase, and in almost all CLL cases, but was not expressed in the vast majority of normal PBL, ALL and ANLL. Normal bone marrow samples appeared to contain a small subpopulation of B-cells which co-expressed GP-70 and SmIg. From those studied it appears that GP-70 is a relatively early B-cell maturation antigen expressed in subpopulations of neoplastic B-cells which populate the peripheral blood in CLL, NHL and HCL. However, GP-70 is not expressed on pre-B type CALL or normal circulating B cells in the peripheral blood.