Suppression of natural killer cell activity in young and old mice

Spleen cells from female mice of the recombinant inbred strain BPS lack natural killer (NK) cytolytic activity, and can suppress the cytolytic activity of normal NK effector cells. The suppressor cells are not typical B cells, T cells, macrophages, or NK cells; they lack the characteristics and surface markers of each of these cell types. In BPS mice, suppressor cell activity is a dominant and significant characteristic of spleen cells at every age tested (2 weeks to 18 months). In other strains of mice which are normally classified as high-responders in NK assays, such as the C57BL strain, these suppressor cells are less prominent but can be detected when separated (on the basis of their higher density) from other spleen cell populations. As mice of the high-responder strains age, however, the suppressor cells become a significant part of the spleen cell population.