Saito, Kazuhisa (Keio University School of Medicine, Tokyo, Japan), Masayasu Nakano, Takehisa Akiyama, and Daizo Ushiba. Passive transfer of immunity to typhoid by macrophages. J. Bacteriol. 84:500–507. 1962.—Cultured peritoneal macrophages collected from mice which had been injected intravenously with intact macrophages of mice immunized with live vaccine were found to exert inhibitory action against intracellular virulent Salmonella enteritidis. This inhibition was quantitatively inferior to that exhibited by peritoneal macrophages from the donors, i.e., mice actively immunized with live vaccine. After an intravenous injection of P32-labeled macrophages into mice, almost no radioactivity could be recovered in the peritoneal exudate cells of the recipients; about 50% of the radioactivity was recovered from the liver, spleen, and mesenteric lymph nodes. Therefore, the inhibitory action of the recipient's peritoneal macrophages against intracellular multiplication was attributed to the capacity of the recipient's own macrophages and not to that of the donor's macrophages. Tissue-cultured macrophages from recipients of sonic-treated cells did not exhibit inhibition against intracellular, virulent S. enteritidis, although the recipients were resistant to intraperitoneal infection with the same strain.