PDX1 and type 1 diabetes mellitus: Isolated islets from NOD.Alox15Δmyel mice revealed an increase in mRNAs levels of Pdx1, which encodes a key transcription factor that promotes β cell function (31), and Cd274, which encodes PD-L1, an immune checkpoint protein that promotes suppression of immune responses in T1D (32) (Figure 3G).