A CELL-SURFACE ANTIGEN THAT CROSS-REACTS WITH MY4, A MONOCLONAL-ANTIBODY TO CD14, IS EXPRESSED ON HUMAN MONOBLASTIC CELL-LINE U937, B-LYMPHOMA CELLS, AND POLYMORPHONUCLEAR LEUKOCYTES

The CD14 antigen was originally identified on monocytes as a different iation marker and usually detected by a panel of monoclonal antibodies , including My4 and LeuM3. Recent studies have shown that CD 14 antige n is expressed on Langerhans cells, a subset of normal B-lymphocytes, neutrophils, and subtypes of B-cell non-Hodgkin's lymphomas. These ant igens, however, react with My4, but not with LeuM3, and the reason for this has not been elucidated. In this study, we found that similar My 4(+)/LeuM3(-) epitopes are expressed on the human monoblastic cell lin e, U937. Northern blotting demonstrated that the U937 cells express ne ither 1.4 kb CD14 transcripts nor possible alternative spliced forms o f CD14 transcripts. The molecule was resistant to phosphatidylinositol specific phospholipase C, which effectively hydrolyzes glycosyl-phosp hatidylinositol anchored protein, decay accelerating factor, on the sa me cells. Lipopolysaccharide, which down-regulates the expression of C D14 on monocytes, did not alter the expression of the molecule. We con cluded that the My4(+)/LeuM3(-) molecule on U937 cells is not CD14 ant igen but another surface protein. A similar molecule was also detected on B-lymphoma cells from a patient with non-Hodgkin's lymphoma and on polymorphonuclear leukocytes from healthy donors.