High levels of MAIT cell activation is evident in the gastrointestinal tissue of patients with IN-COL
There was no significant difference between IN-COL and IN-NAE groups in regard to the MAIT cell count in GMNC (Figure 2ci). IN-COL was associated with a significantly higher proportion of HLA-DR+CD38+ activated MAIT cells (20% of MAIT cells) compared with the IN-NAE group (2%; p>0.01; Figure 2cii). IN-COL was also associated with a greater proportion of granzyme B+ MAIT cells (19% vs 0% of MAIT cells; p<0.05; Figure 2ciii). These changes did not occur in UC. We further confirmed activation of MAIT cells in the tissue by using fluorescently conjugated tetramers to the MAIT TCR ligand (MR1-OP5) and confirmed CD161+tetramer+ T cells were activated in IN-COL (19% HLA-DR+CD38+) but not IN-NAE (0.5%; Figure 2d).
Finally, we confirmed that MAIT cell activation was greater in the gastrointestinal tract than in the peripheral blood by studying paired GMNC and PBMC in IN-COL (N=3) and IN-NAE (N=3). While patients with IN-COL had marginally higher MAIT cell activation measured in PBMCs compared with the IN-NAE group, this difference was more marked in the GMNC samples of 2/3 patients (Figure 2e).