CD4 and Parkinson disease: The reduction in lymphocyte count well before PD in our study is consistent two recent studies, including one that used the UKB dataset (thus validating our approach) [11, 32], as well as a meta-analysis that showed decreased numbers of CD3+ and CD4+ lymphocyte subsets in intermediate and late-stage PD, whilst a decrease in CD8+ T lymphocytes was also observed [56].