Figure 4. Epithelial cells infected by invasive Salmonella Typhimurium do not activate MAIT cells.

(A) MAIT cells are activated by autologous monocytes cultured in the presence of PFA-fixed bacteria (Salmonella enterica serovar Typhimurium (ST)) as assessed by CD69 and CD25 upregulation by Vα7.2⁺CD161^hi cells. Activation was blocked by adding to the culture an anti-MR1 antibody (10 µg/ml). Data are mean and SEM of two independent experiments. * indicates statistical significance for the MOI dose-response curve by 2 way ANOVA. (B) MAIT cells recognize Hela-hMR1 but not Hela cells infected by Ec or ST. Hela and Hela-hMR1 cells were infected by Ec or ST for 30 min before gentamicin treatment to kill extracellular bacteria. Then MACS sorted Vα7.2⁺ cells were cocultured with infected cells overnight. MAIT cell activation was assessed by CD69 and CD25 upregulation of by Vα7.2⁺CD161^hi cells. Data are mean and SEM of three independent experiments. (C) ST ΔSpi1 and ST ΔSpi2 strains were used to infect Hela and Hela-hMR1 cells as in (B). Then MACS sorted Vα7.2⁺ cells were added for overnight culture. MAIT cells activation was assessed by upregulation of CD69 and CD25. Data are mean and SEM of three independent experiments.