Phenotypic expression of genetically controlled host resistance to Listeria monocytogenes

Several inbred mouse strains, all of them derived from the C57BL background, have genetically determined increased resistance to infection with Listeria monocytogenes, whereas a variety of other strains are relatively sensitive to this infection. Comparison of the host response to L. monocytogenes in the sensitive A strain and the resistant C57BL/6 (B6) strain revealed that the B6 mice were superior to A mice both in the T-cell-independent and in the T-cell-dependent phase of the response. Although animals of both strains had equal ability to clear their circulation of intravenously administered Listeria and to take up comparable amounts of bacteria in their livers and spleens, already 24 to 48 h after infection the genetic advantage of B6 strain mice to suppress bacterial proliferation was apparent. Both the primary (early and late) and the secondary responses as well as the ability to inactivate the bacterial load after adoptive protection by syngeneic immune lymphocytes were more efficient in the B6 animals, suggesting that the common effector macrophage arm of the antilisterial resistance rather than the lymphocyte arm (mediating the T-cell-dependent phase of response) is genetically controlled.