PDCD1 and type 1 diabetes mellitus: Serum sPD-1 concentrations were elevated in T1DM patients (<i>P</i> = 0.013) but showed no correlation with glycemic parameters, autoantibody status, or PD-1 genotypes.<h4>Conclusions</h4>PD-1 rs2227981 and rs2227982 polymorphisms are associated with T1DM susceptibility in a Chinese Han cohort.