IL17A and Parkinson disease: In the same study, the death of midbrain neurons derived from autologous induced pluripotent stem cells in PD patients may be closely related to CD4 + Th17 cells secreting IL-17, indicating that in addition to the neuronal susceptibility to CD8 + cytotoxic T lymphocytes, CD4 + T cells are also involved in the pathological process of PD [88].