HLA-DRB1 and chronic obstructive pulmonary disease: When plotting the expression of the top expressed MHC class I-encoding genes (HLA-A, HLA-B, HLA-C, HLA-E) (Figure 4D) and MHC II-encoding genes (HLA-DRA, HLA-DRB1, HLA-DRB5, HLA-DPA1, HLA-DPB1, and HLA-DQB1) (Figure S4E), we found these genes largely to be downregulated in COPD.