Relationship of macrophages to cell-mediated immunity in experimental Nocardia asteroides infection.

Marked in vivo intracellular killing of Nocardia asteroides occurred in the peritoneal macrophages obtained 72 h after an intraperitoneal challenge with N. asteroides, in guinea pigs either actively immunized with ribonucleic acid protein or passively immunized by immune spleen cell transfer from actively immunized donor guinea pigs. This specific killing of N. asteroides in immune macrophages persisted for at least up to 60 days. Administration of antimacrophage sera before intravenous challenge with N. asteroides in the immune guinea pigs produced an early death of the animals, and the total tissue counts of N. asteroides in the liver, spleen, lungs, and heart remained the same in them as in unimmunized controls.