Interleukin-31 and soluble CD40L: new candidate serum biomarkers that predict therapeutic response in multiple sclerosis.

Multiple sclerosis (MS) is a chronic demyelinating autoimmune disease that affects the central nervous system (CNS), varying from relatively benign to severely disabling. Although the roles of several cytokines and chemokines in MS are well established, their roles in MS lesions and evolution remain a matter of debate. Soluble CD40L (sCD40L) is a ligand that induces lymphocyte proinflammatory activity by stimulating the activation and maturation of B cells, promoting isotype switching and affinity hypermutation. Circulating sCD40L levels reflect activation of the CD40-CD40L complex. The interaction between CD40 and CD40L is of fundamental importance, suggesting their role in MS pathogenesis. Interleukin-31 (IL-31) is a proinflammatory cytokine that plays a role in allergies, autoimmune diseases, and is a major factor in several chronic inflammatory diseases. IL-31 triggers the JAK-STAT pathway in several different cell types, to induce proliferation and tissue remodeling in fibroblasts, epithelial cells, and endothelial cells. Some studies have described a correlation between these two cytokines and decreased serum levels of sCD40L and IL-31 after MS treatment, accompanied by a lower inflammatory response. In this review, we emphasize the possible correlation and positive feedback between IL31 and sCD40L in the MS proinflammatory response. We also describe the justification for this hypothesis and whether it is possible to investigate these cytokines as biomarkers of MS.