PDCD1 and autoimmune disease: Distinct human leukocyte antigen (HLA) haplotypes, and polymorphisms in immunoregulatory genes such as CTLA-4 and PD-1 have been associated with a variety of classical autoimmune diseases, and likely play an important role in the development of irAEs (e.g., HLA-DQ8 and HLA-DR53 for lymphocytic hypophysitis), and the predominance of HLA-DR4 among patients treated with PD-1- or PD-L1-directed ICIs developing autoimmune insulin-dependent diabetes (Khan et al., 2018)).