Impaired production of plasma interleukin-6 in patients with Parkinson's disease

The contents of interleukin-6 in the plasma from patients with Parkinson's disease and endogenous depression were compared by enzyme immunoassay. Interleukin-6 content in the plasma increased in the early stage of idiopathic parkinsonism complicated by depressive syndrome. A correlation was found between interleukin-6 content and changes in higher mental activity estimated by neuropsychological tests.