To selectively culture microglia, we used commercially available modified polystyrene (Primaria) plates that allow adherent maintenance of mouse neonatal microglia and human fetal microglia (mNMG and hFMG, respectively) while maintaining the possibility of enzymatic passaging (Supplementary Fig. 1a). In contrast, neuroglial derivatives from neural progenitors are poorly adherent, and thus selected against on this substrate (not shown). IL-34 and CSF1g, important for microglia differentiation and maintenance in vivo 16,17, were added to the medium. Both hFMGs and mNMGs died in the absence of any CSF1R agonist, with hFMGs adopting a more ramified morphology in the presence of high concentrations of IL-34 (Supplementary Fig 1a, b). Primary cells could be maintained in this medium for more than a month without passaging, suggesting this formulation may be generally useful for primary myeloid cultures.
