p24: a human leukemia-associated and lymphohemopoietic progenitor cell surface structure identified with monoclonal antibody

This study was directed at surface structures that are found on human lymphohemopoietic progenitor cells in normal and leukemic bone marrow. A monoclonal antibody was produced against an acute lymphoblastic leukemia (ALL) cell line of the pre-B phenotype; this antibody (BA-2) was used to demonstrate a cell surface polypeptide of ~24,000 mol wt that migrates similarly in both reduced and nonreduced form. This polypeptide, p24/BA-2, was shown by immune precipitation and gel electrophoresis and cell distribution studies to be different from HLA-DR and gp100/cALLa. p24.BA-2 was present on the surface of 77% (54/70) of cases of non-T, non-B ALL; BA-2 staining was less bright or nondetectable in surface Ig⁺ (SIg⁺) chronic lymphocytic leukemia (CLL), and T ALL and nondetectable on peripheral T and B lymphocytes. Approximately 3% of bone marrow mononuclear cells were p24/BA-2⁺, and these cells were E rosette^-, surface (SIg^-), and nonphagocytic. Marrow TdT⁺ progenitor cells were frequently p24/BA-2⁺. Results suggest that p24/BA-2 represents a surface structure present on lymphohemopoietic bone marrow progenitor cells and that most common types of ALL bear the p24/BA-2 structure.