Suppression of interferon gamma production in mice treated with carrageenan

Effects of carrageenan (CAR) treatment on the response of interferon (IFN) production in vivo and in vitro after stimulation with an IFN‐γ inducer, staphylococcal enterotoxin A (SEA), was investigated. The IFN‐γ production in mice stimulated with SEA was impaired after i.v. administration of a 20 mg/kg dose of CAR. Spleen cells (SC) from CAR‐treated mice had decreased ability to produce IFN in vitro after stimulation with the same inducer. SC obtained from mice during the suppressive state inhibited IFN‐γ production when they were co‐cultured with mononuclear cells prepared from spleens of untreated control mice. This suppressor cell activity could be removed from SC by an adherence technique to plastic surface. The SC with suppressor activity were not inactivated by treatments with monoclonal anti‐Thy‐1.2 antibody, anti‐asialo GM1 antisera and anti‐mouse immunoglobulin antisera followed by complement. The suppressive activity was detected in cell‐free culture fluids of macrophage fractions containing suppressor cell activity. These results suggest that the decrease in IFN‐γ production in mice pretreated with CAR may associate with the presence of suppressor cells characterized to the monocytelmacrophage lineage.