Heterologous highly specific antimacrophage serum (AMS) was obtained by immunizing rabbits with macrophage membranes, and subsequently absorbing the antiserum on lymphocytes (in the presence of EDTA). This AMS was highly specific against macrophages as demonstrated by cytotoxicity assays and immunofluorescent staining.
Incubation of macrophages with AMS abrogated their phagocytic activity. This inhibition of phagocytic activity could be reversed by incubating AMS-treated macrophages either in normal serum or in trypsin.
The differences in distribution and location of antigenic determinants on the surfaces of macrophages and lymphocytes was demonstrated by fluorescent staining. Distinct surface antigens, absent on lymphocytes were detected on AMS-treated macrophages.