Various studies indeed suggest the occurrence of peripheral immune changes in PD patients, including decreased CD4+/CD8+ T-cell ratios, fewer CD4 + CD25+ T cells, increased ratios of IFN-γ-producing to IL-4-producing T cells [34], and decreased CD4+ T lymphocytes and CD19+ B cells [35, 36]. The gene discussed is IFNG; the disease is Parkinson disease.