Figure 9.

IL-4-mediated reprogramming of activated microglia increased the recruitment of CCR2⁺ macrophages to the brain. Adult (3 months) male C57BL/6 mice were given an intraperitoneal injection of saline or LPS and 1 h later received an intracerebroventricular (icv) injection of vehicle or IL-4. Enriched microglia were isolated from the brain 24 h after LPS. A, Representative dot plots for CD11b/CD45 staining. Oval indicates peripherally derived macrophages (CD11b⁺/CD45^hi). B, Percentage of CD11b⁺/CD45^hi macrophages (MΦs) associated with the brain (n = 4–7). C, Percentage of CCR2⁺ macrophages that were IL-4Rα⁺ following Saline or LPS treatment alone (n = 3). D, Relative number of CCR2⁺ macrophages associated with the brain out of 10,000 live cells (n = 4–7). E, Proportion of CCR2⁺ macrophages and CCR2 MFI in macrophages of LPS-Veh and LPS-IL-4 groups. A breakdown of the proportion of CCR2^+/− and CX₃CR1^+/− macrophages in LPS-Veh and LPS-IL-4 groups is also shown. F, Partial GFP BM-chimera mice were established on the C57BL/6 background. Mice achieved an average of 60–80% engraftment. After 4 weeks mice were injected with intraperitoneal LPS. Representative series of dot plots showing that >80% of the CD11b⁺/CD45^hi cells identified in A and used for flow analyses were GFP⁺ indicating they derived from a peripheral source. Error bars represent the mean ± SEM. Means with *p < 0.04 are significantly different and means with ⁺p = 0.07 tend to be different from Saline-Vehicle controls. Means with ^#p < 0.05 are significantly different and means with ^‡p = 0.1 tend to be different from LPS-Vehicle.