Fig. 1

Summary of microglia and macrophages in different types of MS lesions. A Lesions are colored where a lighter grey indicates decreased myelin density. Reactive microglia and macrophages are depicted with large cell bodies and are categorized where red indicates decreased, and orange indicates increased expression of what are typically considered homeostatic markers such as P2RY12 or CD163. Reactive microglia and macrophages are also categorized based on whether they contain lipid-rich myelin degradation products. Non-reactivated microglia and macrophages are depicted with small cell bodies and a ramified morphology. B Patterns of microglia and macrophage characteristics (density, ramification, and homeostatic marker expression) over time in different MS lesion types. EA (D) early active (demyelinating), LA (D) late active (demyelinating), MAI (D) mixed active–inactive (demyelinating), MAI (PD) mixed active–inactive (post-demyelinating), I inactive. For A and B, active (post-demyelinating) lesions are not depicted due to limited histopathological assessments of microglia and macrophage characteristics