MHC class II positive microglia and lymphocytic infiltration are present in the substantia nigra and striatum in mouse model of Parkinson's disease

We have studied MHC class II antigen expression and lymphocytic infiltratio n during dopaminergic neurone degeneration produced by intoxication with 1- methyl-4-phenyl-1,2,3,6-tetrahydropiridine (MPTP). Microglial activation wa s observed in the striatum and in the substantia nigra (SN) in this model. We noticed a marked increase of MHC class II antigen expression on microgli a and T-cell recruitment in these regions after MPTP treatment. B-lymphocyt es were not observed. T-cell infiltration predominantly consisted of CD8+ c ells at every time point but CD4+ cells were present too. More than a half of the observed lymphocytes showed strong staining of CD44 antigen. Our fin dings suggest a possible immune system involvement in the pathological proc ess following MPTP intoxication.