Although, whether CD8+ Teffs recognize cognate antigen in PD is uncertain, the increased clonality of the TCR repertoire in PD patients suggests that antigen-specific CD8+ Teff responses triggered by CNS antigens lead to increased release of proinflammatory mediators, such as IFN-γ and TNF-α, as well as perforins and granzymes that contribute to chronic neuroinflammation and neurodegeneration [87]. Here, IFNG is linked to Parkinson disease.