Circulating interleukin-10 and interleukin-12 in Parkinson's disease.

Interleukin (IL)-12 is a heterodimeric cytokine produced by activated blood monocytes, macrophages and glial cells. It enhances differentiation and proliferation of T cells and increases production of proinflammatory cytokines. IL-10 is a pleiotropic cytokine produced by both lymphocytes and mononuclear phagocytes including microglia. Recent studies demonstrated the neuroprotective effect of IL-10. There is little information about the involvement of IL-12 or IL-10 in the pathophysiology of Parkinson's disease (PD). The objective of our study was to assess the role of IL-12 as a potential marker of immune reactions in patients with PD and to investigate whether IL-10, an immunosuppressive cytokine, may have a neuroprotective effect in the pathogenesis of PD. We measured using immunoassay serum IL-12 and IL-10 levels in 41 patients with PD in comparison with serum levels in 19 healthy subjects (controls) age and sex matched. IL-12 and IL-10 levels were tested for correlation with sex, age, disease duration, Hoehn and Yahr stage and the UPDRS III score. The PD group presented with significantly increased IL-10 levels when compared with the control group (P = 0.02). The increase observed was not affected by the treatment status. A strong and significant correlation between IL-10 and IL-12 levels was observed in patients with PD (R(S) = 0.7, P < 0.000001). Our findings suggest that IL-10 may be involved in the pathogenetic mechanisms of PD. The elevation of IL-10 and the significant correlation between IL-10 and IL-12, a proinflammatory cytokine, may suggest that immunological disturbances and neuroprotective mechanisms are involved in patients with PD.