In the paediatric cohort, the proportion of CD8+CD27+ MAIT cells was decreased and that of CD8−CD27− MAIT cells increased in children with type 1 diabetes compared with control children (median 63.9% vs 67.1% of MAIT cells, p = 0.04, and median 4.6% vs 3.1% of MAIT cells, p = 0.004, respectively; Fig. 2b, c), while the CD8+CD27− and CD8−CD27+ MAIT cell subsets remained unaltered (ESM Fig. 3). This evidence concerns the gene CD27 and type 1 diabetes mellitus.