Mo2: functional properties of antigen-bearing cells

Mo2 is a membrane antigen whose expression is associated with human cells enriched for monocytes and macrophages. Anti-Mo2 monoclonal antibody in the presence of rabbit complement causes an inhibition of the proliferative response of human peripheral blood leukocytes (PBL) to soluble antigens, that can be restored by the addition of fresh monocytes. Fluorescence-activated cell sorting (FACS) of PBL on the basis of Mo2 expression results in a population of Mo2+ cells (morphologically monocytes) that is selectively active in phagocytosis and cytolysis of antibody-sensitized human erythrocytes, and a population of Mo2- cells (morphologically lymphoid cells) that is nonphagocytic but selectively active in natural killing. These experiments indicate that expression of Mo2 is a useful marker for cells possessing the morphological and functional properties of monocytes.