Increase in peripheral CD4 bright+ CD8 dull+ T cells in Parkinson disease

Background: immune abnormalities are known to be involved in the pathogenesis of sporadic Parkinson disease. Objective: To examine whether abnormalities in peripheral lymphocytes exist in Parkinson disease. Methods: Immune mediators, including CD1a, CD3, CD4, CD8, CD45RO, and Fas (CD95), were examined in peripheral lymphocytes of patients by 3-color flow cytometry. Results: Patients with Parkinson disease displayed a significantly greater population of circulating CD3 CD4 bright(+) CD8 dull(+) lymphocytes than age-matched control subjects (P=.005) and patients with cerebrovascular disease (P=.002). The increase in these cells appeared to continue for at least 17 months. These T cells also expressed CD45RO and Fas, markers for activated T cells, while CD1a, a marker for thymic T cells, was negative, suggesting that these cells are mature T cells with immune activities. Conclusions: As CD4(+) CD8(+) T cells are known to increase after some specific viral infections, the continuous increase in CD4 bright(+) CD8 dull(+) T cells shown here may indicate postinfectious immune abnormalities that are possibly associated with the pathogenesis of this slowly progressive, multifactorial neurodegenerative disease.