Immunity in Parkinson's disease - the role of adaptive and auto-immune responses and gut-microbiome axis

Parkinson's disease (PD) is the second most common neurodegenerative disorder. It is characterised by loss of dopaminergic neurons in the mid-brain and accumulation of α-synuclein aggregates referred to as Lewy bodies. PD is a progressive disease and the treatments available are aimed at addressing only its symptomatology. Immune dysregulation is one of the several mechanisms that are hypothesized to contribute towards PD pathogenesis. This review firstly addresses the interaction of innate and adaptive immune components and the role of adaptive immune responses, with a particular focus on T lymphocytes in PD. The review secondly examines the evidence for the involvement of the autoimmune system in PD, including the presence of autoantibodies and the association of autoimmunity with proteins linked with PD (α-synuclein and neuromelanin) and with infections. The review thirdly explores the connection between the gut microbiota the immune system and the impact of this relationship on the pathogenic processes of PD. Finally, this review discusses adaptive immunity based therapeutic strategies for PD, probable PD detection approaches based on autoimmunity, and the potential of gut-microbiome replenishment in PD treatment.