PDCD1 and neurodegenerative disease: In this study, we aimed to clarify the role of PD-1 in neurodegenerative disease by analysing the impact of a genetic deletion of PD-1 in a model of prion disease, which combines misfolded protein accumulation and neurodegeneration (Obst et al., 2017), and where neuroinflammation plays a critical role (Gomez-Nicola et al., 2013).