Murine natural suppressor cells in the newborn, in bone marrow, and after cyclophosphamide. Genetic variations and dependence on IFN-gamma.

Natural suppressor (NS) cells are potent, Ag nonspecific, MHC-unrestricted inhibitors of immune responses. Murine NS activity is found in several situations, including adult bone marrow (BM) and neonatal/newborn spleen, and spleen following total lymphoid irradiation, after BM transplantation and after cyclophosphamide (CY) treatment. Using three of these situations (adult BM, newborn spleen, and spleen after CY treatment), the strain distribution of NS cell activity was assessed. A wide variation in potency is seen in both naturally occurring (adult BM and newborn spleen) and induced (after CY treatment) NS cell activity. Up to 10-fold differences in NS activity are seen between high and low NS strains. This reflects an intrinsic genetic variation between mouse strains in both naturally occurring and CY-induced NS cell activity. Thus, a strain with high NS activity at birth, has high NS activity in its BM as an adult and in its spleen after CY treatment. Of the strains tested, B10.D2 has the highest NS cell activity while BALB/c has the lowest, and the F1 between these two strains is intermediate in NS activity. Finally, the NS cell activity from all strains tested required IFN-gamma for expression of its inhibitory activity.