Fig. 6

Microglia expressing MHC-II are associated with pSyn inclusions in the agranular insular cortex. a–c Representative images of pSyn accumulation in the agranular insular cortex at 2, 4, and 6 months p.i. Pathology is primarily localized to the soma at 2 months (a), with increased neuritic pathology by 4 months (b) and an observable decrease overall by 6 months, possibly due to death of neurons. c No pSyn inclusions were observed in PBS-injected animals (g–i). d–f A similar pattern was observed in MHC-II expression on microglia. Peak numbers of MHC-IIir microglia were observed at 2 months p.i. (d), decreased at 4 months (e), and virtually absent by 6 months (f). j–l Few to no MHC-IIir microglia were observed in PBS injected animals at any time point, suggesting that MHC-II expression occurs in response to accumulation of pSyn inside neurons. Abbreviations: p.i. = postinjection; pSyn = α-syn phosphorylated at serine 129; PFFs = pre-formed alpha-synuclein fibrils; PBS = phosphate-buffered saline; MHC-II = major-histocompatibility complex-II; ir = immunoreactive