Immunocytochemistry was performed using a rabbit polyclonal anti-P2Y12 antibody10 (link) (generated by Dr. H. Weiner, Harvard University, Cambridge, MA), a monoclonal anti-CD68 antibody (Dako, Burlington, Ontario, Canada; 1:100), and appropriate secondary antibodies. For human brain sections, slides were deparaffinized and antigen retrieval was performed using a 0.01 M sodium citrate buffer solution (pH 6.0) for 15 minutes in the microwave on high setting.