NATURAL SUPPRESSOR CELLS FOR MURINE NK ACTIVITY

Abstract

This chapter discusses the presence of suppressor cells in some natural situations and their possible role in the physiologic regulation of natural killer (NK) activity. In mice, NK activity is absent at birth, begins to appear around 3 weeks of age, peaks at 6–8 weeks, and declines to low levels after 12 weeks of age. The low NK activity of spleen cells of aged mice was not associated with detectable suppressor cells. Normal mice of various inbred strains have been shown to vary considerably in their levels of spontaneous NK activity. Murine NK activity has a characteristic tissue distribution, with relatively high NK activity present in the spleen and peripheral blood and little or no activity in the thymus or peritoneal cavity. The frequent association between low NK activity and suppressor cells suggests that inhibition by macrophages or other cells at the effector phase may account for, or at least contribute to, the low cytolytic activity. The presence of suppressor cells in the peritoneal cavity, a site with low NK activity, but not in the spleen, an organ with high NK activity, suggests a possible regulatory role for these cells.