The increase in OPN have been demonstrated in many inflammatory autoimmune diseases, such as multiple sclerosis, glomerulonephritis, Crohn's disease, and systemic lupus erythematosus (SLE) (19, 28–31), which suggests that OPN plays a significant role in the pathogenesis of these inflammatory autoimmune disease. Here, SPP1 is linked to systemic lupus erythematosus.