a, Schematic of young (3–4 months) mice injected intraperitoneally with CCL11 or vehicle, and in combination with anti-CCL11 neutralizing or isotype control antibody. b, Representative field of Dcx-positive cells for each treatment group (n = 6–10 mice) treated four times over ten days. (scale bar: 100μm). c, Quantification of neurogenesis in the DG after treatment. d, Schematic of young adult mice given unilateral stereotaxic injections of anti-CCL11 neutralizing or isotype control antibody followed by systemic injections with either recombinant CCL11 or PBS (vehicle). e, Representative field of Dcx-positive cells in adjacent sides of the DG for each treatment group (n = 3–11 mice) f, Quantification of neurogenesis in the DG after systemic and stereotaxic treatment. g,h, Learning and memory assessed by contextual fear conditioning (g) and RAWM (h) paradigms in young adult mice injected with CCL11 or vehicle every three days for five weeks (n = 12–16 mice per group). All data represented as Mean ± SEM; *P< 0.05; **P<0.01; ANOVA, Dunnet’s or Tukey’s post-hoc test (c,f); repeated measures ANOVA, Bonferroni post-hoc test (k).