The effect of colloidal carbon on the organ distribution of sheep red cells and the immune response.

The organ distribution, blood clearance rate, and immune response to intravenous Cr-labelled sheep red blood cells (SRBC) have been studied in mice, following administration of a single intravenous dose of colloidal carbon. In normal mice 80–90 per cent of SRBC were found in the liver and 2–6 per cent in the spleen. The blood clearance rate of SRBC was extremely rapid. Colloidal carbon caused a marked depression of hepatic uptake of SRBC and a corresponding increase in splenic uptake. This effect was maximal at 6 hours after carbon administration and recovery of hepatic phagocytosis occurred over 4 days. The rate of clearance of SRBC was greatly reduced while the hepatic uptake of red cells was depressed. At low doses of cells there was an increase in titre of humoral antibody and in numbers of spleen PFCs while, at high doses of cells, a slight depression in immune response occurred. `Stimulation' of splenic uptake of antigen and of the immune response by colloidal carbon is associated with depression of hepatic phagocytosis.