Functional alterations of peripheral blood CD4+ T lymphocyte subsets in patients with Parkinson disease: A review

Parkinson disease (PD) is a neurological degenerative disorder common among the elderly. Neuroinflammation leads to neurodegeneration, which is regulated by the peripheral adaptive immunity. This review discusses the regulatory roles of neuroinflammation by CD4 + T cell subsets (T helper [Th] cell 1, Th2, Th17, Th9, and regulatory T cells). First, we emphasized the roles and mechanisms of CD4 + T cell subsets, as well as the cytokines they secrete, in PD. Second, we explore the associations between helper T cells, regulatory T cells, core cytokines (interleukin 2, 6, 8, tumor necrosis factor-α, interferon-γ), and chemokines (monocyte chemoattractant protein-1) and PD and clarify the role of peripheral inflammation in disease progression. Finally, analyzing the operation of CD4 + T cell subsets in the nervous system will facilitate the development of new therapeutic interventions.