Th17 Cell Pathogenicity Promoted by Integrin α3 During Autoimmune Neuroinflammation

Autoimmune diseases are caused by dysregulated immune responses against self. Multiple sclerosis (MS) is one such autoimmune disease in which the central nervous system (CNS) is affected by chronic inflammation, and Th17 cells are critical mediators of disease pathogenesis. While targeting leukocyte trafficking is effective in treating autoimmunity, there are currently no therapeutic interventions that specifically block encephalitogenic Th17 cell migration. Here, we report integrin α3 as a Th17 cell-selective determinant of pathogenicity in experimental autoimmune encephalomyelitis, a mouse model of MS. CNS-infiltrating Th17 cells express high integrin α3, the expression of which is induced by transcription factors that are required for Th17 cell specification. The deletion integrin α3 in CD4+ T cells or IL-17A-fate-mapped cells attenuated disease severity. Mechanistically, integrin α3 promoted the polarization, proliferation, and transmigration of Th17 cells, and integrin α3-deficiency enhanced the retention of CD4+ T cells in the perivascular space of the blood-brain barrier. Notably, differential RNA-seq expression analysis revealed that Th17 cells continuously depend on integrin α3 to maintain Th17 cell identity and effector function. The requirement of integrin α3 in Th17 cell pathogenicity suggests integrin α3 as a therapeutic target for MS treatment.