D11, a novel monoclonal antibody specific for human mature macrophages and peripheral blood monocytes

A new monoclonal antibody designated Mab D11 is described, which shows a restricted reactivity to cells of the monocyte/macrophage system. When tested by light and electron microscopic immunoperoxidase methods, Mab D11 specifically reacts with blood monocytes and stains resident macrophages in a wide variety of human tissues; it does not mark the macrophages of other species, i.e., rat, swine and mouse. Antigen-presenting cells, e.g., Langerhans cells, are Mab D11 negative. Mab D11 reveals the antigen on cryostat and paraffin tissue sections. Ultrastructurally the antigen recognized by Mab D11 in all macrophage types studied is located on the plasma membrane and within cytoplasmic structures including lysosomes. On immunoblotting, Mab D11 detects the 125-kDa antigen in human liver and the 135-kDa protein in tumours of histiocytic origin. The similarity of Mab D11 to known "pan-macrophage" monoclonal antibodies is discussed.