Indeed, IL-21 levels are increased in the peripheral blood and tissues of patients with systematic lupus erythematosus (SLE), rheumatoid arthritis (RA), type 1 diabetes (T1D), immune thrombocytopenia (ITP), primary Sjogren's syndrome (pSS), autoimmune thyroid disease (AITD) and psoriasis.
In conclusion, the expression of IL-21 and IL-21R were up-regulated in AITD and may be involved in the pathogenesis of the disease through augmenting aberrant immune cascade.