The use of macrophages stimulated by immune interferon as indicator cells in the mononuclear phagocyte assay

Macrophages obtained from human monocytes by monolayer culture were stimulated with recombinant immune interferon. They were compared with unstimulated macrophages and monocytes as indicator cells in the mononuclear phagocyte assay, using both IgG anti-Rh(D)-coated complement-coated red cells. The presence of the interferon in the culture medium improved the adherence of macrophages in monolayers. The interferon markedly augmented the number of IgG-coated red cells which became attached to the macrophages and reduced the amount of antibody needed for red cell-macrophage interaction. This stimulatory effect occurred regardless of the IgG subclass composition of the anti-Rh(D) antibody. The activity of the stimulated macrophages to interact with IgG- or complement-coated red cells was considerably greater than that of monocytes. The results imply that macrophages treated with recombinant immune interferon are more sensitive than monocytes as indicator cells in the mononuclear phagocyte assay.