Antigen handling in aging. II. The role of Kupffer and endothelial cells in antigen processing in Fischer 344 rats.

A method has been developed for the purification of Kupffer and endothelial cells from rat liver by collagenase enzyme perfusion followed by centrifugal elutriation. After intravenous injection of a soluble antigen, [3H]azoaniline bovine serum albumin ( [3H]BSA), its distribution was studied in isolated cell populations from liver and spleen tissue of two aged groups of male F-344 rats. In young adult rats (6-8 months) both sinusoidal cell types contained the same amount of [3H]BSA; however, in older rats (22-24 months) the amount of antigen in the endothelial cells was significantly decreased. In comparison to the liver, the spleen retained only a small fraction of the injected dose. In order to assess the catabolic properties of both Kupffer and endothelial cells, supernatants obtained from in vitro cell culture were evaluated for both biological and physiochemical properties. Antigen was almost completely degraded by both cell types as determined by gel filtration and did not directly stimulate BSA-primed lymphocytes in vitro; however, these supernatants were shown to enhance the lymphoproliferative response of primed lymphocytes to additional antigen exposure. Kupffer cell receptors, Fc and C3, assayed by direct rosetting, did not vary with age; endothelial cells also possessed Fc receptors that were found to be unchanged with age. These studies are an initial attempt to better define our previous finding of defective antigen handling with aging by use of isolated pure cell populations.