The role of suppressive macrophages in influenza virus-induced immunosuppression.

To confirm the role of macrophages in influenza virus (IV)-induced immunosuppression (IS) of mice, silica, a selectively destructive agent for macrophages, was tested for its ability to influence the IV-induced IS. Silica completely abolished that effect. In contrast, Indomethacin--a prostaglandin inhibitor--did not influence the IV-induced IS. Peritoneal macrophages of mice infected with IV were suppressive for plaque forming cell (PFC) response of normal spleen cells in vitro. The assumption was made that suppressive macrophages were induced by IV in mice. However, no suppressive factors were found in the culture fluid of these cells.