For instance, immune infiltrating cells CD8+ and CD4+ T cells, which were significantly different in PD samples compared with control animal models (Brochard et al., 2008; Harms et al., 2017), were related to dopaminergic neuron cell loss in the PD group (Brochard et al., 2008; Williams et al., 2021). The gene discussed is CD8A; the disease is Parkinson disease.