CD4 and Parkinson disease: PD animal models show that DR3-deficiency in CD4 T cells protect mice from 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced neurodegeneration [122], while high levels of dopamine triggers the secretion of anti-inflammatory cytokine IL-10 in CD4 T cells through stimulating DR2 [123].