Abstract
BACKGROUND AND PURPOSE: Peripheral inflammation is probably involved in the pathogenesis of progressive supranuclear palsy (PSP) and it may be a common feature with Parkinson's disease (PD). The peripheral immune profile in PSP remains unclear, as well as whether the inflammatory pathways differ from those in PD. The neutrophil-to-lymphocyte ratio (NLR) has been proven to be a well-established biomarker of systemic inflammation. This study aimed to evaluate the peripheral immune profile in PSP compared with PD. METHODS: A cross-sectional study was conducted including patients with PSP and PD and healthy controls (HCs). Leukocyte subpopulations and the NLR were measured in peripheral blood. Multivariate linear regression and post hoc tests were applied. Electronic databases were searched in November 2023 to perform meta-analyses to clarify the peripheral immune profile in PSP. RESULTS: Our cohort included 121 patients with PSP, 127 patients with PD and 266 HCs. The NLR was higher in PSP and PD compared with HCs. PSP had a higher neutrophil count compared with HCs. Whilst a lower lymphocyte count was found in PD compared with HCs, the lymphocyte count did not differ between PSP and HCs. The meta-analyses supported this immune profile. CONCLUSIONS: PSP and PD show an increased peripheral inflammation and a higher NLR compared with HCs. Different pathogenic inflammatory mechanisms are probably involved in PSP and PD, since in PSP this altered peripheral immune profile is mainly driven by neutrophils. Understanding the neutrophils' role in PSP may allow for the development of targeted therapies.