Activated microglial cells are found within the substantia nigra in autopsied PD patients, and increased levels of proinflammatory cytokines such as tumor necrosis factor α (TNF-α), interleukin 6 (IL-6) and interleukin 1β (IL-1β) are also found in the substantia nigra in PD [42]. This evidence concerns the gene IL1B and Parkinson disease.