Failure of FK 506 to suppress the T cell-mediated immunity of mice to Listeria monocytogenes.

Listeria monocytogenes belongs to the group of intracellular bacteria, which means that they reside and multiply within host cells. The protective immunity against such an infection is mediated by cellular immune mechanisms. Whereas the CD8+ T cell population plays a major role therein, the CD4+ T cells are held to be of minor importance in this defence system. Consequently, one can understand that immune suppression with FK 506 which acts primarily on this latter T cell subset, does not interfere with protective immunity of mice infected with L. monocytogenes. We have demonstrated that the drug blocks neither curing of primary infection, nor formation of granulomas, nor induction of cell populations capable of mediating adoptive transfer of immunity, nor expression of pre-existing immunity.