Expression of CD 19 antigen on acute monoblastic leukemia cells at diagnosis and after TPA-induced differentiation

We have previously shown that CD 19, a B-lymphoid differentiation antigen, is expressed on acute myeloid leukemia cells. In this study, the expression of CD 19 and CD 14 (a monocytic antigen) was investigated in 18 cases of acute monoblastic leukemia. The staining by anti-CD 19 antibody (SB4) ranged between 26 and 81% of the cells, and was significantly correlated with the staining by anti-CD 14. Double stainings confirmed that the antigens were expressed on the same cells. After a 48-hr culture in the presence of TPA, most cells became adherent and lost CD 19 antigen, whereas CD 14 was still expressed with only minimal changes. It is concluded that CD 19 antigen is expressed on more immature stages of monoblastic leukemias. The hypothesis that CD 19 could be an early monocytic differentiation antigen is discussed.