The protective role of T-cell receptor V gamma 1(+) T cells in primary infection with Listeria monocytogenes

We have previously reported that the T-cell receptor (TCR) gamma delta(+) T cells increase in mice infected with an intracellular bacteria Listeria monocytogenes, and the cells predominantly express V delta 6 and V gamma 1 genes. In this study, we used a monoclonal antibody (mAb) specific to TCR V gamma 1 to estimate the frequency of V gamma 1(+) T cells and we discuss their significance in protection against L. monocytogenes. The spleen, liver and peritoneal exudate cells from mice intraperitoneally infected with L. monocytogenes were analysed by flow cytometry. In all the organs investigated, V gamma 1(+) cells increased predominantly among TCR gamma delta(+) T cells at an early phase (day 5-7) of the infection. To elucidate the significance of the V gamma 1(+) T cells in the protection against L. monocytogenes, mice were depleted of TCR V gamma 1(+) gamma delta T cells or all TCR gamma delta(+) T cells by intraperitoneal inoculation of anti-V gamma 1 mAb or anti-pan TCR gamma delta mAb, respectively, before infection with L. monocytogenes. The bacterial growth in the spleen and the liver examined on day 5 after the infection increased significantly by the depletion of TCR V gamma 1(+) Tc ells. The numbers of L. monocytogenes in TCR V gamma 1(+) T-cell-depleted mice were nearly the same as in mice depleted of all TCR gamma delta(+) T cells. These results demonstrated that V gamma 1(+) T cells are the predominant population of gamma delta T cells in protection against L. monocytogenes at the early phase of the primary infection.