Although the endogenous levels of IFNγ in healthy human brain are known tobe virtually undetectable (Frugier et al., 2010), allelicdifferences between early- and late-onset PD patients were reported for theIFNγ gene, a provocative finding that may influence infiltration of T-cellsduring progression of the disease since T-cells are the major producers of IFNγ. Here, IFNG is linked to Parkinson disease.