SUMMARY
MAIT cells are an abundant T-cell population enriched in peripheral tissues such as the liver. They are activated both through TCR-dependent and - independent mechanisms. However, the different specific functional responses of MAIT cells to these distinct signals remain elusive. We examined the impact of combinations of TCR-dependent and -independent signals in blood and tissue-derived human MAIT cells. TCR-independent activation of MAIT cells from blood and gut was maximised by extending the panel of cytokines to including TNF-superfamily member TL1A. RNAseq experiments revealed that TCR-dependent and -independent signals drive MAIT cells to exert overlapping and unique effector functions, impacting both host defence and tissue homeostasis. While TCR-triggering alone is insufficient to drive sustained activation, TCR-triggered MAIT cells did show specific enrichment of tissue-repair functions at the level of gene expression, protein production and in in vitro assays and these functions were amplified by cytokine costimulation. Taken together, these data indicate the blend of TCR-dependent and -independent signalling to MAIT cells may play a role in controlling the balance between healthy and pathological processes of tissue inflammation and repair.
Footnotes
1.Tested the normality of all presented data-sets using Kolmogorov-Smirnov tests. Used nonparametric tests when at least one dataset from an experiment did not pass the normality test. 2.Combined all the main cytokine-only data from previous Figures 1 and 2 in new Fig1: new data from Hossain/Philipp replaced previous Figures 2A-D + featuring the analysis of CD69 expression 3.Moved previous Fig1D and Fig2E into Supplementary Fig1 4.Combined newly generated TCR-related (5-OPRU and aCD3/28) data into new Fig2 5.Combined previous Figures 1C, 1E and 1F 6.Removed previous Subfigures 5A and 5B 7.Rearranged remaining subfigures from previous Fig5 into new Fig3 and added results of the statistical analyses showing the effect of E.coli stimulation on CD8+ MAIT cells isolated either form blood or gut. 8.Reorganized previous Supplementary Fig4 into new Supplementary Fig3. Added new data showing the effect of MR1-blocking on MAIT cell activation with the e.coli model. 9.Removed gMFI analyses for PD-1 and CD39 from Fig6 and rearranged remaining subfigures into new Fig4 10.Moved RNAseq data previously shown in Fig3 to new Fig5 and added new volcano plots comparing, C vs T, TC vs T and c vs TC 11.Marked genes from the tissue-repair list that are significantly altered in at least one comparison in blue: THBS1, PDGFB, FURIN, CSF1, PDGFA, CCL3, TNF, VEGFA, HBEGF, MMP24 and FGF9 12.Marked selected inflammation-associated genes (IFNG, IL17F, IL26, OSM, IL12RB2, LAG3) in red, altered Figlegend to include the description of the blue/red marked genes. 13.Merged previous supplementary Fig2 with Fig4 A-C to create new Supplementary Fig4. in support of new Fig5. 14.Moved all tissue-repair-related data from previous Fig4 into new Fig6. GSEA plots - New data showing the expression of Furin, CCL3 an TNF by MAITs after 72h of E.coli stimulation - Scratch assays with Caco2 cells 15.New supplemental Fig5 corresponding to new Fig6. Relative expression of the genes belonging to the tissue repair gene set present in our data in MAIT cells stimulated by TCR or TCR+cytokines. Leading edge genes have been marked. 24h expression of Furin, CCL3 an TNF by MAITs & 24h and 72h our expression of GM-CSF by MAITs after E.coli stimulation 16.Created a compilation of examples showing our normality testing - SF2C, F1G and F3A 17.Updated the Materials and Methods section to include additional methods, antibodies and cell lines used in new experiments