XBP1 and rheumatoid arthritis: Transcription factors and other markers indicative of ER-stress, such as IRE1α, CHOP, PERK, and XBP1, have been found to be deregulated in systemic lupus erythematosus (SLE) and scleroderma (SSc) (6), XBP1 mutations or deletions in animal models have been associated with inflammatory bowel disease (IBD) (7), and impaired ER-Golgi transport has been associated with lupus nephritis and rheumatoid arthritis (RA) (8).