IFNG and Parkinson disease: The cytokines chosen for assessment were interferon‐γ (IFNγ), tumour necrosis factor‐α (TNFα) and interleukin‐1β (IL‐1β) as these cytokines are linked to both MHC II induction (Dong and Benveniste, 2001) and PD pathogenesis (Mogi et al., 1994a, 1994b; Mount et al., 2007).