PDCD1LG2 and type 1 diabetes mellitus: Moreover, NOD mouse models lacking PD-L1 or PD-L2 and bone marrow chimera experiments have provided additional evidence that the PD-L1 expressed on non-hematopoietic cells is essential for preventing rapid-onset T1D in mice, whereas PD-L2 is not (Keir et al., 2006).