Augmentation of natural killer cell activity in spleens of infant, aged, and low responder strain mice by Corynebacterium parvum.

: Murine natural killer (NK) cell activity is both age- and strain-dependent. NK activity does not appear in murine spleen cells until three weeks after birth. Activity peaks at approximately 10 weeks, decreasing thereafter with mice over one year old showing significantly reduced levels. Mice showing low or no NK activity because of age (aged and infant mice, respectively) can be stimulated to show significant levels of NK lysis by i.p. injection of formalin killed Corynebacterium parvum (CP). In addition, CP treatment is also capable of increasing NK activity in mice from the normally low responding AKR strain. The NK activity induced or stimulated by CP appears to be like normal NK reactivity in that it is not decreased by removal of T-cells or adherent cells. Thus, in addition to increasing NK activity in normally responsive mice, CP is capable of augmenting NK activity in mice which normally show low or no levels of NK lysis.