Lipoprotein-induced inhibition of plaque-forming cell generation and natural killer cell frequency in aged donors.

The in vitro effects of human high-density, low-density and very-low-density lipoproteins on plaque-forming cell generation and natural killer cytotoxicity were evaluated in 40 aged donors. Lipoprotein pretreatment led to a significant inhibition in plaque-forming cell capacity displayed by either peripheral blood mononuclear cells or purified lymphocytes. As far as natural killer cytotoxicity is concerned, such pretreatment decreased the number of natural killer cells bound to targets, while the lytic efficiency was unaffected in both 51Cr-release and agarose-single-cell cytotoxic assays. These data suggest a role for lipoproteins in the impairment of cell-mediated immunity in elderly individuals.