Carrageenan stimulates the release of dialyzable helper factors

We found that 1 mg of carrageenan (CGN) could enhance the primary antibody response of BALB/c spleen cells to sheep erythrocytes (SRBC). This enhancement was dependent on the strain of mouse injected as well as the type of CGN administered. In vitro experiments with spleen cells from mice treated with CGN in vivo showed that these cells release low molecular weight factor(s) which enhanced the in vitro antibody response to SRBC. Thy 1+ cells were clearly involved in the production of this factor since depletion of these cells eliminated the helper effect of CGN-treated spleen cells. Our results suggest one possible mechanism by which CGN can modulate the immune response.