Selective macrophage cytotoxicity of carrageenan in vivo.

The suggestion that carrageenan suppressed the cutaneous manifestation of established delayed hypersensitivity (DH) by macrophage cytotoxicity could not be supported histopathologically. In a dose more than sufficient to suppress DH, carrageenan was undetectable by histochemical means in the macrophages of sple-n, lymph nodes, or bone marrow. It required concentrations of carrageenan threefold higher than the immunosuppressive dose to be detected in the above locations. Under no circumstances was macrophage cytotoxicity observed in these sites.