A monoclonal antibody recognizing the p150/95 leucocyte differentiation antigen.

A monoclonal antibody KB90 recognizing a molecule containing two polypeptide subunits of 140 and 98 kd is described. Biochemical studies following high pH dissociation of the molecule showed KB90 to bind to an epitope on the 140 kd subunit. The molecule recognized by KB90 appears to correspond to the p150/95 molecule in the family of leucocyte differentiation antigens of which the LFA-1 and Mac-1 molecules are members. Analysis of the immunocytochemical reactivity of KB90 shows that it stains monocytes, tissue macrophages, granulocytes and a small population of lymphocytes. These reactions are clearly distinct from those of the LFA-1 and Mac-1 molecules.