Peritoneal cells obtained from mice immunized 15 or 30 days previously with (i) 0.1 LDw of attenuated Salmonella typhimurium (RIA), (ii) 20 jug (dry weight) of heat-killed Salmonella (SR-11), (iii) 20 Ag (dry weight) of immunogenic ribosomal subfractions, or (iv) 20 Ag of ribonucleic acid (RNA) subfractions were passively transferred to normal unimmunized mice. The ability of the recipient animals to inhibit or retard the multiplication of virulent challenge S. typhimurium 5 days postinfection

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... as determined by pathogen counts on the carcasses. Peritoneal cells from donors immunized with the RIA, ribosomal, or RNA preparations (i) conferred maximal resistance to challenge 10 to 15 days after cell transfer and demonstrable resistance throughout the 45-day assay period, (ii) conferred resistance to infection when 105, 103, or 102 peritoneal cells were injected subcutaneously but not with fewer than 105 cells administered intraperitoneally, and (iii) rendered recipients capable of acting as donors of peritoneal cells that conferred demonstrable resistance on normal recipients. Recipients of peritoneal cells obtained from donors immunized with heat-killed bacteria were unable to (i) significantly inhibit bacterial proliferation at 10 days post-transfer, (ii) resist infection by a challenge inoculum greater than 50 on May 7, 2020 by guest http://iai.asm.org/ Downloaded from on May 7, 2020 by guest http://iai.asm.org/ Downloaded from