IL17A and Arthritis: IL-17 has been implicated in (1) animal models of PANDAS, (2) subtypes of arthritis in our PANS or PANDAS cohort, (3) pediatric OCD, and (4) psoriasis.26,54 In murine models, repeated GAS infection has been shown to induce a robust Th17 response in nasal-associated lymphoid tissue.26 This model showed that GAS exposure promoted migration and persistence of GAS-specific Th17 cells to the brain, leading to neurovascular dysfunction.