Fig. 2a summarizes the protocol and the timeline used to generate microglia-like cells from human ES and iPS cells. When harvested and plated separately on Primaria, semi-adherent cells appear vacuolated, round and motile, and stain positive for PU.1, as well as CD11b and IBA1 (AIF1) ((Fig. 2b,c, Supplementary Movie 1). These markers have been extensively used to label or define microglia in various systems 24. These cells can be further sorted by FACS and are homogeneously positive for IBA1, CD45 and CD11b (Fig 2d, e), with the majority of cells physically selected by the growth conditions positive for all markers. We went on to characterize these immature cells and their progeny, which we refer to as pluripotent stem cell-derived microglia-like cells (pMGLs). The immature pMGLs initially delaminating from YS-EBs are round yet already highly phagocytic, as observed by the uptake of fluorescent latex beads and the appearance of filopodia and membrane ruffles, allowing the capture of nearby corpuscles such as inert plastic beads (Fig. 2f, g and Supplementary Movies 1, 2). The cells are highly motile and will readily tax to and encapsulate foreign bodies such as fibers present in the well (Fig. 2f).
