CD38 and Parkinson disease: The IVW analysis revealed that the genetically predicted level of three immune cell proteins per standard‐deviation increase was positively associated with PD, including CD38 (OR = 1.13, 95%CI: 1.05–1.22, P = 0.001), FcγRIIIB (OR = 1.06, 95%CI: 1.01–1.11, P = 0.019), and CUL4B (OR = 1.11, 95% CI: 1.00–1.20, P = 0.012) (Figure 2).