Homeostatic and pathological processes in the gut and the brain are closely interconnected. Accordingly, inflammatory bowel diseases (IBD) predispose for neurodegenerative diseases and a number of neurological disorders are associated with changes in the intestinal environment, indicative for gut-brain inter-organ communication. Although a crucial role of targeted immune cell trafficking for gut and brain inflammation is evident, it is unclear, whether and by what mechanisms immune cell trafficking contributes to gut-brain interaction. This project aims to unravel the cellular substrates of gut-to-brain-communication in the context of neurodegeneration in Parkinson’s disease by elucidating the cell trafficking circuits of T cells along the gut-brain axis in preclinical models and human patients. Moreover, we aim to determine the mechanisms underlying such gut-to-brain cell trafficking, and to explore therapeutic interventions to target it. This knowledge will open novel avenues towards the treatment of intestinal and neurological diseases.