TRIM21 and systemic lupus erythematosus: hTRIM21 was originally discovered as an ‘autoantigen’ (RO52 or SS-A) in patients with systemic lupus erythematosus (SLE) (Ben-Chetrit et al., 1988), and its increased expression was also found in Sjögren’s syndrome (Ben-Chetrit et al., 1990).