CD28 and Parkinson disease: The depletion of naive T cells (CD95−) was associated with weakened immune protection in the elderly and clonal expansion of CD28-T cells, which may acquire cytotoxicity under certain conditions.[54] The reduced number of Tdg cells is consistent with lower numbers in the peripheral blood of PD patients reported in 1 study[55] and corroborated by bioinformatics analysis of significant differences in PD immune cell fractions.[56] However, contradictory results have also been reported,[57] so further studies are required to confirm Tgd cell changes in PD.