Ym1 responder microglia subset. Microglia cells were extracted from the cortices of mice treated for 16 h intracerebroventricularly with vehicle or IL4, purified by immunosorting using CD11b-loaded magnetic beads and analyzed by fluorescence-activated cell sorting for Ym1 protein expression. (A) CD11b-positive cells were characterized before purification and show a specific forward and side scatter profile with respect to other brain cells. (B) After immunosorting, IL4 treatment is ineffective in inducing Ym1 expression in the microglia-depleted fraction (upper panel). Conversely, IL4 induces an increase in Ym1 expression in CD11b-positive cells (lower panel). (C) Quantitative analysis of the number of Ym1-positive microglia cells shows that a significant percentage of cells (≈25%) is induced by the IL4 treatment. *: P < 0.05; n = 3.