In accordance with the beneficial role of this cytoprotective enzyme, different polymorphisms in the Hmox1 promoter region determine different levels of HO-1 induction, associated either with protective functions or with increased susceptibility towards autoimmune and inflammatory diseases, such as rheumatoid arthritis (RA) or systemic lupus erythematosus (SLE) (84). Here, HMOX1 is linked to rheumatoid arthritis.