Effect of carrageenan on the induction of cell-mediated cytotoxic responses in vivo.

Carrageenan (CAR), a sulphated polygalactose having macrophage toxic properties, elicited a suppression of primary cytotoxic T lymphocyte (CTL) responses against allogeneic tumour cells in the spleen when the tumour cells (EL-4 tumour cells, H-2b) were administered subcutaneously to AKR mice. When the allogeneic tumour cells were administered intravenously to AKR mice, no CTL responses to the alloantigens were detected in the spleen, but were detected in the peritoneal exudate cells, and CAR treatment suppressed the responses. On the other hand, in vitro secondary CTL responses of cells from alloantigen-primed mice were markedly enhanced by the pre-treatment of such mice with CAR. These results may suggest that two steps, macrophage-dependent and independent, are involved in the development of CTL responses in vivo.