Cell-mediated immune response to Salmonella typhimurium infection in mice: development of nonspecific bactericidal activity against Listeria monocytogenes.

Generation of the cell-mediated immune response of CBA/H mice against Salmonella typhimurium (C5S) was monitored by measuring the nonspecifically increased bactericidal activity of macrophages against Listeria monocytogenes. The appearance of detectable levels of macrophage activation was inversely related to the initiating infectious dose. With 3 X 10(3) infecting C5S organisms, significant activity was demonstrable after day 3. Immunity controlled a challenge with a streptomycin-resistant strain of S. typhimurium (C5R) successfully only by approximately day 7. In the period of increasing activity against L. monocytogenes, growth of C5R was only delayed. Since such an effect could not be demonstrated in Listeria-infected mice, these findings suggest that immunity against C5R necessitates specific factors besides macrophage activation.