Fig. 1. F. tularensis LVS activates MAIT reporter cells via MR1 in vitro and induces systematic MAIT cell expansion in vivo.

A Jurkat.MAIT-AF7 and C1R.MR1 cells were co-incubated for 16 h with indicated amounts of 5-OP-RU, F. tularensis lysate (in PBS), PBS, F. tularensis culture supernatant, or media control (BHI). For infection samples, we co-cultured Jurkat.MAIT-AF7 for 16 h with C1R.MR1 cells that had been infected at the indicated MOI for 4 h, in the presence of gentamicin. Activation was detected by staining with anti-CD69 antibody. Anti-MR1 antibody (26.5) or isotype control (W6/32) was added, as indicated, to C1R.MR1 cells 2 h prior to co-incubation with Jurkat.MAIT cells. Experiment was performed on two separate occasions with similar results. Data show mean fluorescence intensity (MFI) (mean ± SEM of triplicate wells from one experiment). Statistical tests: unpaired t-test (two-tailed) comparing S/N, lysate, and MOI 100 groups with their respective controls, and one-way ANOVA with Dunnett’s multiple comparisons, comparing anti-MR1 and isotype control with unblocked samples. P-values are indicated. B Flow cytometry plots and C MAIT cell percentage in αβ-T cells from the liver, lung, spleen, kidney, and blood (200 μl) of C57BL/6 mice either uninfected or intravenously infected with 10⁴ CFU F. tularensis LVS for 14 days. D, E Absolute numbers of MAIT cells and non-MAIT αβ-T cells, respectively, in the liver, lung, spleen, kidney, and blood (200 μl) of C57BL/6 mice either uninfected or intravenously infected, 14 days post infection. The experiment was performed twice with similar results. Data show mean ± SEM n = 5 mice from one experiment. Statistical tests: unpaired t-test (two-tailed) comparing uninfected with infected mice. p-values are indicated. See also Supplementary Figs. 1 and 2. Source data are provided as a Source Data file.