Impairment of lymphocyte proliferative responses and interleukin-2 production in susceptible (C57BL/6) mice infected with Salmonella typhimurium.

C57BL/6 (susceptible) and A/J (resistant) mice were infected intravenously with a temperature-sensitive mutant of Salmonella typhimurium. In C57BL/6 mice a marked depression of the proliferative response of spleen cells to B and T mitogens occurred and was maximal at 2-3 weeks post-infection, whereas only minor changes were found in A/J mice. This immunodepression was mediated, at least in part, by adherent cells. Moreover, spleen cells from infected C57BL/6 mice did not produce interleukin-2 (IL-2) after concanavalin A stimulation. The impairment of IL-2 production was not related to a defect in IL-1 release. The addition of IL-2 to spleen cells did not restore their ability to respond to mitogens. The depression of mitogenic responses in infected C57BL/6 mice occurred at a time when increased resistance was present.