Reduced proliferative response of mouse spleen cells to mitogens during infection with Salmonella typhimurium or Listeria monocytogenes.

A significant reduction in the mitogenic responsiveness (uptake of 3H-thymidine) of murine spleen cells to concanavalin A, phytohemagglutinin or lipopolysaccharide was observed during infection with virulent Salmonella typhimurium. The decreased response to mitogens could be observed independent of the immunity to typhimurium (Ity) genotype, i.e. in CBA/J mice and C3H/HeJ mice (Ityr) as well as in C57BL/6 mice (Itys). Because reduced responsiveness was demonstrated in C3H/HeJ mice, which are susceptible to S. typhimurium infection but are unresponsive to lipopolysaccharide, it is concluded that the two phenomena are not correlated with one another. A similar decrease in response to mitogens was shown in mice infected with Listeria monocytogenes. Reduction in mitogenic responsiveness was directly correlated with the number of viable bacteria detected in the spleen cell suspension. Decreased lymphoproliferation could be observed as early as 2 days after infection and lasted 3 weeks in sublethally infected mice. The question remains whether or not the reduced responsiveness indicates an enhanced susceptibility to infection or merely represents a high degree of activation of defense mechanisms.