The protective role of T-cell receptor Vgamma1+ T cells in primary infection with Listeria monocytogenes

Abstract

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 Vdelta6 and Vgamma1 genes. In this study, we used a monoclonal antibody (mAb) specific to TCR Vgamma1 to estimate the frequency of Vgamma1+ 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, Vgamma1+ 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 Vgamma1+ T cells in the protection against L. monocytogenes, mice were depleted of TCR Vgamma1+ gamma delta T cells or all TCR gamma delta+ T cells by intraperitoneal inoculation of anti-Vgamma1 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 Vgamma1+ T cells. The numbers of L. monocytogenes in TCR Vgamma1+ T-cell-depleted mice were nearly the same as in mice depleted of all TCR gamma delta+ T cells. These results demonstrated that Vgamma1+ T cells are the predominant population of gamma delta T cells in protection against L. monocytogenes at the early phase of the primary infection.

Figure 1

TCR Vγ1 expression of TCR γδ T cells in the spleen cells, hepatic lymphocytes and PEC from L. monocytogenes-infected mice analysed by flow cytometry. Mice were infected i.p. with 1×10³ of L. monocytogenes. On day 5, lymphocytes from the spleen, liver and peritoneal cavity were stained with FITC-conjugated anti-TCR Vγ1 mAb, PE-conjugated anti-TCR-Cδ mAb, and APC-conjugated anti-CD3 mAb and analysed by FACSCalibur. The analysis gate was set on CD3⁺ cells, and the profiles of TCR γδ and TCR Vγ1 expression in CD3⁺ cells are shown. The data shown are representative of data from individual analysis of 20 mice.

Figure 2

Kinetics of TCR Vγ1⁺ T cells in the spleen, liver and peritoneal cavity after L. monocytogenes infection. Spleen cells, hepatic lymphocytes and plastic plate-non-adherent PEC were prepared as mentioned in the Materials and Methods from mice i.p. inoculated with 1×10³L. monocytogenes at the indicated intervals after the infection, and examined as described in Fig. 1. Percentages of Cδ⁺ cells and Vγ1⁺ cells in the CD3⁺ population are demonstrated in the upper panels (a, b and c). The cell numbers of the T-cell subsets per mouse were further calculated based on the number of lymphocytes harvested per mouse and the percentage of TCR γδ⁺ or TCR Vγ1⁺ cells, and demonstrated in the lower panels (d, e and f). The data of spleen cells (a, d), hepatic lymphocytes (b, e) and PEC (c, f) are shown. Open symbols and closed symbols represent the data of TCR γδ⁺ T cells and TCR Vγ1⁺ T cells, respectively. The data shown are the summaries of data from individual analysis of 12 mice. *P <0·05 compared to the data on day 0.

Figure 3

Kinetics of percentage of TCR Vγ1⁺ T cells in total TCR γδ T cells in the spleen, liver and peritoneal cavity. Spleen cells, hepatic lymphocytes and plastic plate-non-adherent PEC were analysed as described in Fig. 2. Results are expressed as the percentages of TCR Vγ1⁺ T cells in the TCR γδ⁺ T-cell population. The data shown are the summaries of data from individual analysis of 12 mice. *P <0·05 compared to the percentage of Vγ1⁺ T cells on day 0.

Figure 4

Depletion of TCR Vγ1⁺ T cells or TCR γδ⁺ T cells after administration of anti-TCR Vγ1 or anti-pan TCR γδ mAb. Mice were i.p. inoculated with anti-TCR Vγ1 mAb 2·11 or anti-pan TCR γδ mAb UC-7 2 days before infection with 1×10³L. monocytogenes. PEC and spleen cells were obtained on day 7 after mAb administration and stained with FITC-conjugated anti-TCR Vγ1 mAb, PE-conjugated anti-TCR γδ mAb and APC-conjugated anti-CD3 mAb as described in the Materials and Methods. All panels show the profile of TCR γδ and Vγ1 expression in CD3⁺ cells. The data shown are representatives of data from individual analysis of 10 mice.

Figure 5

Effects of administration of anti-TCR Vγ1 or anti-pan TCR γδ mAb on elimination of bacteria from the spleen and liver. Mice were treated with 0·25 mg of anti-TCR Vγ1 or anti-pan TCR γδ mAb on day −2 and i.p. infected with 1×10³L. monocytogenes on day 0. The numbers of L. monocytogenes in the spleen and liver were determined on day 5 of the infection. Values are means±SD for groups of four mice. Two independent analyses showed nearly the same result. The results shown are representatives of the analysis. *P <0·05 compared to control.