Fig. 1. CD8⁺ Treg cells mediate suppression of STZ-induced diabetes by H. polygyrus.

a–c Mice were administered STZ at 14 days after infection with Hp. a Blood glucose concentrations were monitored, b plasma insulin was measured, and c pancreatic sections were stained with an anti-insulin antibody at 14 days after T1D induction. Representative histological images are shown (left panels), and a bar graph depicts the percentage of the stained area observed under a microscope (right panel). d CD8⁺ Treg cells defined as CD8⁺CD122⁺ cells in the pancreatic LN from mice before and at 14 days after infection with Hp were quantified by flow cytometry. The numbers indicate the percentages of CD8⁺ Treg cells in the FSC/SSC-gated lymphoid cells. e Kinetics of the absolute number of CD8⁺ Treg cells in the pancreatic LN. f–h Hp-infected mice were administered an anti-CD122 antibody immediately before and after T1D induction. f Spleen cells of these mice were assessed for the depletive effects of the antibody on CD122-expressing cells by flow cytometry. The effects of this manipulation on blood glucose (g), plasma insulin levels (h), and pancreatic β-cells (i) were evaluated as described in a–c. j Blood glucose of mice that received CD8⁺ Tregs or non-Treg CD8⁺CD122^- cells was monitored after injection of STZ. k TCR-driven proliferation of CD4⁺ (left panels) and CD8⁺ T (right panels) cells in the presence or absence of antigen-presenting cells cultured with CD8⁺CD122⁺ cells from the indicated mice at the indicated ratio was evaluated by flow cytometry. l Cytokine concentrations were quantified in supernatants of the cultured cells in k. Values represent the mean ± SD of 15 mice (sum of three repeated experiments, five mice each). Experiments in l and k were repeated three times, and values represent the mean ± SD of 10 mice (sum of three repeated experiments, three or four mice each). Asterisks denote statistical significance at p < 0.05 calculated by the two-way ANOVA (a, e, g, j) and Tukey post-hoc analysis (b, c, h, i, k, l). Scale bars indicate 40 μm (c, i). All experiments were repeated at least three times with similar results.