TNF and Parkinson disease: Significant increases in innate immune factors, including interleukin (IL)-1, IL-2, and IL-6 and tumor necrosis factor (TNF)-α, have been detected within the substantia nigra pars compacta (SNpc) and cerebrospinal fluid (CSF) of PD patients (24, 25), and γδ T cells, the first line of defense, have also been found to be elevated within the peripheral blood and CSF (26).