Osteopontin in autoimmune disorders: current knowledge and future perspective.

Osteopontin (OPN) is a multifunctional cytokine and adhesion molecule, as well as an unusual regulator for both innate and adaptive immune responses. Several immune cells can produce OPN, including dendritic cells (DCs), macrophages, and T lymphocytes. OPN expression is reported to be increased in a wide range of disorders, including autoimmunity, cancer, and allergy. The overexpression of OPN in several autoimmune disorders, such as rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), multiple sclerosis (MS), Type 1 diabetes (T1D), inflammatory bowel disease (IBD), Sjögren's, and myasthenia gravis, have been shown to be correlated with disease severity. Regarding the important regulatory roles of OPN in the immune system, this study aimed to review the role of this molecule in autoimmune disorders and to provide a complete view of the current knowledge in this field.