RAG1 and Parkinson disease: T-cell activation and infiltration of the substantia nigra and striatum have been observed in MPTP models (Chandra et al., 2017).This result is also supported by recent studies carried out with T-cell receptor (TCR) β chain–deficient mice, SCID mice, and recombination-activating-gen-1 (RAG1) knockout (Rag1−/−) mice, which demonstrated that T-cell deficiency results in a strong attenuation of dopaminergic neurodegeneration in MPTP-induced PD (Brochard et al., 2009).