Distribution of a new B-cell-associated surface antigen (BL7) detected by a monoclonal antibody in human leukemic disorders.

A murine monoclonal antibody (anti-BL7) was raised by immunization of BALB/c mice with a precursor B-cell line (Josh-7) which detects a heat-stable, nonimmunoprecipitable antigen. The expression of BL7 was investigated in peripheral blood and/or bone marrow leukemic cell suspensions stained by indirect immunofluorescence and analyzed by flow cytometry. Lymphoblasts from 43 of 43 cases of "null" acute lymphoblastic leukemia were BL7-. Five cases of T-acute lymphoblastic leukemia and 5 cases of terminal deoxynucleotidyl transferase-positive blastic chronic myelogenous leukemia were also BL7-. All 63 cases of B-cell chronic lymphocytic leukemia were BL7+. Neoplastic cells in 22 of 28 cases of B-cell non-Hodgkin's lymphomas in leukemic phase were also BL7+. Expression of BL7 showed some correlation with Rappaport's histological classification. Four cases of multiple myeloma and plasma cell leukemia were BL7-. Twenty-three cases of acute nonlymphocytic leukemias were also analyzed. Of these, only the acute promyelocytic (M3,4 cases) and acute myelomonocytic (M4, one case) varieties expressed BL7 on a small proportion (approximately 15%) of the leukemic cells. All other subgroups were BL7-. The reactivity of anti-BL7 was compared to other B-cell antibodies on selected samples and was shown to be different from B1, B2, and the BA antibodies. Anti-BL7 is a unique monoclonal antibody useful in the study of B-cell cancers.