Lymphocyte populations in Parkinson's disease and in rat models of parkinsonism

To assess the involvement of the immune system in Parkinson's disease we st udied the phenotype of circulating lymphocytes in 30 untreated and 34 treat ed patients. We found a numeric decrease in helper T cells (higher in CD4()CD45RA(-) than in CD4(+)CD29(+)) and B cells, and a rise in activated, CD4 (+)CD25(+) lymphocytes that was correlated with lymphocyte depletion. All t hese alterations were independent of levodopa treatment. In addition, we pe rformed striatal dopamine depletion in rats with either MPP+ or 6-OHDA, sho wing that MPP+ but not 6-OHDA can increase CD4(+)CD25(+) lymphocytes. Thus, mechanisms other than dopamine deficit may explain the immune activation i n Parkinson's disease. (C) 2001 Elsevier Science B.V. All rights reserved.