Expression of LCN2—a common indicator of gut inflammation, PTPRC which encodes CD45—an immune cell marker,CD8B—a cytotoxic T-cell marker, and SNCA which encodes α-synuclein—a protein involved in PD pathology—was higher than in HCs (p = 0.0093, p = 0.0413, p = 0.0140, p = 0.0366, respectively) (Fig. 1B). Here, CD8B is linked to Parkinson disease.