The mechanism of the adjuvant effect of dextran sulphate.

Intravenous dextran sulphate caused an increase in the humoral response to suboptimal doses of sheep red cells (SRBC) in mice. Dextran sulphate of molecular weight 900,000 accumulated in Kupffer cells and caused a reduction in the ability of liver to clear SRBC from the bloodstream. Concomitant increase in uptake of SRBC by the spleen was linearly related to increase in the humoral immune response. These effects were not seen after injection of sulphated polysaccharides of molecular weight less than 20,000 or after neutral dextrans. Dextran phosphates and DEAE—Dextran caused redistribution of injected SRBC and increase in the immune response.