With a high proinflammatory potential, IL-21 is linked to the development of autoimmune diseases and inflammatory disorders, and plays a role in reactive thrombocytosis [86] Furthermore, IL-21 was produced by almost all Th1 and Th17/Th1 cells specific for β2GPI, a key target for antiphospholipid antibodies in antiphospholipid syndrome. This evidence concerns the gene IL21 and antiphospholipid syndrome.