PDCD1 and type 1 diabetes mellitus: On the other hand, since some commensal bacterial strains modulate the response to anti-PD-1 therapy, the alteration of microbiota composition found in T1D patients could be directly or indirectly responsible for a defect of the PD-1-PD-L1 inhibitory pathway leading to reduced islet-reactive T cell exhaustion, enhanced activation of TRM cells in pancreatic tissue and β cell damage.