TREM2 and infarction: These findings imply that following infarction and the breakdown of the blood‐brain barrier, TREM2‐positive CD68‐negative monocytes invade the brain parenchyma at the site of the injury (consistent with the role of TREM2 expression in chemotaxis 30), differentiate into TREM2‐positive CD68‐positive macrophages that became, over a period of about a week, phagocytic CD68‐positive TREM2‐negative macrophages.