Role of T-cell subsets in protection, delayed type of hypersensitivity and granuloma formation during Yersinia enterocolitica infection in mice.

Studies were undertaken with (C57BL/6 x DBA/2) B6D2 F1 mice as a prototype of a strain resistant to Y. enterocolitica. The growth of Y. enterocolitica in liver and spleen following intravenous infection was determined. Restriction of growth of Y. enterocolitica in the spleen and liver started, when a delayed type of hypersensitivity (DTH) became elicitable. Mice were treated with monoclonal antibodies (mAb) specific to T-cell surface markers; injection of these antibodies leads to marked depletion of the specific T-cell subset. After selective in vivo depletion the three characteristic T-cell mediated phenomena, DTH, anti-bacterial protection and granuloma formation were investigated. DTH to Y. enterocolitica soluble antigen was abolished in mice treated with anti-Thy1.2 or anti-CD4 mAbs, while anti-CD8 mAbs had no effect. The elimination of bacteria from the spleens of infected animals was inhibited by the application of either anti-Thy1.2 or anti-CD8 mAbs, while anti-CD4 mAbs had a marginal effect on anti-bacterial protection. The accelerated development of mononuclear cell foci in the liver of immune mice was also inhibited by the application of anti-CD4 and anti-CD8 mAbs. Thus, it appears that specific T-lymphocytes play an important role in murine Yersiniosis. The present model is valuable for the investigation of the cellular immune response to this important enteric pathogen.