The opposite was true for expression of Human Leukocyte Antigen DPα1 (HLA-DPα1), a MHC protein known to be present on activated infiltrating microglia: a disease-dependent increase in HLA-DPα1 mRNA expression being observed with PD development (Fig. 2, early and late PD cases, 1.73 ± 0.23 and 1.80 ± 0.20 fold change from control respectively, p > .05 and p < .05). Here, HLA-DPA1 is linked to Parkinson disease.