CD200 and Parkinson disease: Mitochondria have been the subject of intensive research in PD, following the discovery that chemical inhibition of complex I (CI) of the mitochondrial respiratory chain (MRC) can cause a parkinsonian phenotype in humans and other primates, with dopaminergic neuron loss and inclusions resembling LP in the SNc (Langston et al., 1983; Ramsay et al., 1986; Betarbet et al., 2000).