HLA-DRA and chronic obstructive pulmonary disease: Differential expression of MHCII genes showed an increase in several MHCII genes, namely HLA-DQA1, HLA-DRA, HLA-DOB and HLA-DOA, in either moderate or severe COPD cores or both compared with control cores, with no differences in mild COPD cores (Table 2, Figure 3B).