A re-evaluation of the role of macrophages in carrageenan-induced immunosuppression.

Administration of a single dose of 1 mg carrageenan to mice cause a temporary blockade of hepatic phagocytosis of 51Cr-labelled sheep erythrocytes (SRBC) and a prolonged reduction in the number of splenic plaque-forming cells (PFC) against SRBC. The in vitro responses to phytohaemagglutinin (PHA) and SRBC were also suppressed, whereas the response to the T cell-independent antigen DNP-Ficoll was not affected. Other in vitro experiments have shown that responses of normal cells can be actively suppressed by macrophages from carrageenan-treated mice and the possible mechanisms of this suppression are discussed.