In addition, the involvement of some accessory immune cells that results key players in the CD4+ T-cell mediated inflammation associated to MS should be considered in PD, such as γδT-cells, which strongly inhibit the suppressive activity of Tregs in the central nervous system (127), or peripheral macrophages infiltrating the brain, which results much more relevant than microglia promoting neuroinflammation in response to GM-CSF (128). This evidence concerns the gene CD4 and Parkinson disease.