CD38 and Parkinson disease: More precisely, our results showed that higher percentages of resting CD4 regulatory T cells (%CD4 + T cells) and IgD-CD38-B cells (% lymphocytes) were associated with a lower risk of PD (IVW OR, 0·91 (95 % CI 0·85, 0·99), P= 0·033 and 0·96 (95 % CI 0·93, 0·99), P= 0·038, respectively).