PDCD1 and type 1 diabetes mellitus: Additional findings from the study of Shan et al. were: (i) positive correlation of the frequencies of PD-1+CD8+ Tem cells with fasting serum C-peptide levels (r = 0.4308, p < 0.05) and C-peptide levels 2 h after meal in T1DM patients (r = 0.5723, p < 0.01); (ii) negative correlation of the frequencies of PD-1+CD8+ Tem cells with the levels of glycated hemoglobulin (HbA1c) (r = −0.2992, p < 0.05); (iii) significant reduction in frequencies of PD-1+CD8+ Tem in the intervention group treated with anti-PD-1 mAbs compared to the control group (14.22 ± 6.455% vs. 27.69 ± 9.837%, p < 0.05) [43].