HLA-C and rheumatoid arthritis: The association of RA-induced pulmonary fibrosis also involves MHC gene loci on chromosome 6, such as HLA-B54, HLA-DQ1B*0601, HLA-B40, and sites encoding a-1 protease inhibitors, which are associated with increased ILD risk in patients with RA (Spagnolo et al., 2014).