NGF and Parkinson disease: Finally, we employed a mediator MR design to identify the mediating effects of 731 immune cell phenotypes in the onset of PD.<h4>Results</h4>Elevated levels of Fas cell surface death receptors (<i>p</i> = 0.015) and nerve growth factor (<i>p</i> = 0.026) are associated with a reduced risk of PD, while increased levels of thrombomodulin (<i>p</i> = 0.028) are a risk factor for PD.