Fig 1: Differential activation of T cells by diverse ligands presented by MR1 allomorphs.A, representative flow cytometry panels showing MAIT cell intracellular staining with anti-IFNγ (y axis) or anti-TNF (x axis) antibodies after stimulation with MR1 allomorph C1R cell lines, C1R.MR1null cells or C1R parental cells in the presence or absence of 1 nM 5-OP-RU. B–D, histograms display the percentage of TNF (B), IFNγ (C) or CD69 (D) expression among MAIT cells (TRAV1-2+CD161+) incubated with MR1 allomorph cell lines pulsed with 5-OP-RU titrated 10-fold from 1 nM or in the absence of ligand. Colour-coded wedges correspond to 5-OP-RU titration from top dose to zero. E–G, histograms display the intensity (MFI) of TNF (E), IFNγ (F), or CD69 (G) from MAIT cells as above. Data are from one experiment with three healthy blood donors. Dots represent individual donors; bars represent mean and error bars are ± standard deviation. H, representative flow cytometry panels showing intracellular staining with anti-IFNγ (y axis) or anti-TNF (x axis) from expanded MR1R9H-pyridoxal tetramer-reactive T cells cultured alone (grey) or after stimulation with C1R.MR1null cell lines transduced with MR1∗01 (black), MR1∗04:01 (dark purple) pulsed with 200 μM pyridoxal (top panels) or in the absence of exogenous ligand (bottom panels). I and J, paired analyses display the percentage of TNF (I) or IFNγ (J) expressing T cells after stimulation as above. Data are from four separate healthy blood donors. Dots represent individual donors; bars represent mean and error bars are ± standard deviation. Statistical significance was determined using a two-way ANOVA with Sidak’s multiple comparison test.