Fig. 1.

T_reg responses during Listeria infection display a biphasic kinetic pattern. C57BL/6 mice infected with L. monocytogenes ΔactA-Ova. (A) Number of CD25⁺FoxP3⁺CD4⁺ T_regs in spleens 0 to 9 d postinfection (n = 4 to 8 per group). (B and C) In vitro CD45.1⁺CD8⁺ T_resps proliferation/percent suppression at day 3 after coculture with CD45.2⁺CD4⁺FoxP3-eGFP⁺ T_regs isolated from naïve Foxp3^eGFP mice and those that underwent 1, 3, or 7 d of infection. Indicated are titrated T_reg:T_resp ratios after anti-CD3/CD28 stimulation (n = 4 per group). Reported in histograms are percentage and data from 1:1 T_reg:T_resp cocultures. Mean ± SEM; (A and B) *P < 0.05, **P < 0.01, and ***P < 0.001 (Student’s t test); (B) ^††P < 0.01 and ^††††P < 0.0001 (one-way ANOVA relative to −T_reg). CTV, CellTrace Violet; NS, not significant.