Suppression of murine natural killer cell activity by adherent cells from aging mice.

Natural killer (NK) cell activity declines with age in mice. The purpose of this study was to investigate the effect of peritoneal and splenic adherent cells from young and old mice on NK activity to determine whether adherent cell suppressor function might contribute to this decline. Peritoneal adherent cells from old mice suppressed NK activity of young splenic non-adherent indicator cells more than peritoneal cells from young mice. Splenic adherent cells from old but not from young mice also suppressed this activity. That (1) the suppressive activity of the adherent cell populations was not affected by treatment with anti-Thy-1 plus complement, and that (2) the adherent cell population contained 77-92% cells positive for alpha-naphthyl acetate esterase activity, suggests that the active adherent suppressor cell may be a macrophage. Therefore, the age-related decline in NK activity in mice can be explained, in part, by an increase in adherent cell suppressor function.