Detection of monocyte specific antigen on human acute leukaemia cells

Heteroantisera with specificity for human monocyte and macrophage antigens (HuMa) have been tested for activity against peripheral blood cells from patients with acute leukaemia. Using indirect immunofluorescence, blast cells from 25/27 patients with acute myelomonocytic leukaemia were reactive with anti-HuMa antisera, whereas blasts from 19/20 patients with acute myeloblastic leukaemia and 13/13 patients with acute lymphoblastic leukaemia were not reactive. The F(ab1)2 fragment of the antibody retained specific activity. Activity of whole serum against myelomonocytic blast cells was specifically removed by absorption with macrophages. These observations indicate that circulating blast cells from patients with acute myelomonocytic leukaemia may carry differentiation antigens characteristic of monocytes and macrophages.