TNF and Parkinson disease: Activated forms of the resident immune cells of the central nervous system, microglia, have been found in the brains of PD patients at post-mortem (McGeer et al., 1988), while elevated levels of pro-inflammatory cytokines such as tumor necrosis factor-alpha (TNF-α), interleukin (IL)-1β and IL6 have been measured in the cerebrospinal fluid of patients (Mogi et al., 1994a, Mogi et al., 1994b, Blum-Degen et al., 1995, Muller et al., 1998).