The monoclonal antimonocyte antibody My4 stains B lymphocytes and two distinct monocyte subsets in human peripheral blood.

The monoclonal antibody (MAB) My4 was produced against human myelo-monocytic leukemia cells and stains regular monocytes with high intensity. Employing logarithmic amplification in immunofluorescence flow cytometry an additional low intensity - My4+ - and a very low intensity population - My4(+) - can be identified. Light scatter analysis reveals monocyte features for the My4++ and for the My4+ cells, while the My4(+) cells exhibit characteristics of lymphocytes. The two low intensity (My4+ and My4(+)) populations are clearly discernable only after two color immunofluorescence analysis using MABs VEP13 (CD16) and B1 (CD20). The My4+ cells coexpress the CD16 antigen and comprise a unique monocyte subset. The My4(+) cells coexpress the B1 antigen, characteristic of B cells. In addition, the My4(+) cells are depleted after treatment of mononuclear cells with the anti-B cell MAB BA-1 plus complement. Finally, leukemic cells from patients with B cell type chronic lymphocytic leukemia are stained in 18/20 cases. Hence, the MAB My4 identifies regular monocytes and in addition, with lower intensity of staining a new monocyte subset and a subset of B cells in human peripheral blood.