The analysis of PD-1 expression after three days of PMA-ionomycin stimulation, revealed a significant lower percentage of CD8+PD-1+ cells and in particular CD8+PD-1high cells in the LT T1D group analyzed in respect to the control group (Fig 4A, Kruskal–Wallis one-way analysis of variance p = 0.0099; 4b, Kruskal–Wallis one-way analysis of variance p = 0.0018), while there was no difference in the CD8+PD-1low percentages among the three study groups (Fig 4C, Kruskal–Wallis one-way analysis of variance p = 0.5888). This evidence concerns the gene PDCD1 and type 1 diabetes mellitus.