Fig 2: TL1A Enhances the Activation of MAIT Cells Suboptimally Stimulated with IL-12 and IL-18CD8+ T cells were enriched from healthy peripheral blood mononuclear cells (PBMCs) and stimulated overnight with different combinations of cytokines: IL-12 at 2 ng/mL, IL-18 at 50 ng/mL, IL-15 at 25 ng/mL, and TL1A from 0.01 to 100 ng/mL as indicated.(A–C) Proportions of CD8+ MAIT/CD161+ or CD161− cells producing IFN-γ (A), TNF-α (B), or CD69 (C) following overnight stimulation with suboptimal concentrations of IL-12 and IL-18, plus varying concentrations of TL1A.(D) Representative histograms showing the expression of IFN-γ, TNF-α, GrB, and CD69 by MAIT cells after stimulation with different combinations of cytokines.(E–H) Frequency of MAIT cells expressing IFN-γ (E), TNF-α (F), GrB (G), and CD69 (H) upon stimulation with the indicated cytokines.Data were acquired from seven donors in 2–3 experiments. Error bars represent means ± SEM. Differences among conditions were analyzed by Friedman tests with Dunn’s multiple comparison tests. ∗p < 0.05, ∗∗p < 0.01, ∗∗∗p < 0.001, ∗∗∗∗p < 0.0001.See also Figure S1.

Fig 3: MAIT Cells Can Be Found Close to and within the Colonic Epithelium(A–G) Representative images showing the expression of Va7.2, CD161, CD8, PLZF, CD3, and CD103 in the lamina propria and the epithelium of fixed samples of colonic polyp tissue. Samples were mounted on cytometer chips and iteratively stained with sets of three directly fluorochrome-conjugated antibodies as described in the methods section. Depicted are a merged picture (A) and all the individual stains for Va7.2 (B), CD161(C), CD8 (D), PLZF (E), CD3 (F), and CD103 (G). White arrows mark cells showing co-expression of Va7.2, CD161, PLZF, and CD3 that were defined as MAIT cells here. Note that while CD8 was co-expressed in most of them, CD8− MAITs (arrow + asterisk) could also be found. In contrast, CD103 was rarely co-expressed on MAITs (arrow + diamond). During the iterative staining process dust particles and other detritus can be picked up by the solution flowing over the tissue creating autofluorescent artifacts (1–4). While some of these get washed away after completion of the staining cycle (1, 4), others present during multiple imaging rounds (2, 3). Scale bars, 50μm.