HLA-DRB1 and type 1 diabetes mellitus: Interestingly, a recent study showed that GAD65- and IGRP (islet glucose-reactive protein)-specific CD4+ T effector and T regulatory cells (Tregs) were present at higher frequencies in the peripheral blood of HLA-DRB1*15:01-DQA1*01:02-B1*06:02 positive individuals (i.e. negatively associated with T1D) compared to subjects with neutral or T1D-susceptible alleles28.