EAE was induced in C57BL/6 (H-2^b) mice by immunization with MOG peptide 35-55 on day 0. From day 0–10, mice were treated with a neutralizing anti–IL-3 mAb (anti–IL-3, 50 μg/day) or purified rat IgG (Control, 50 μg/day) and analyzed on day 11. A third group of C57BL/6 (H-2^b) mice was not immunized with MOG peptide 35-55 and not treated with antibodies (no EAE). (A) On day 11, leukocytes infiltrating the brain were quantified by flow cytometry (n = 9–10/group). Blockade of IL-3 reduced cerebral monocytes and total leukocytes (CD45⁺) by more than 50 %. Cerebral CD4⁺ and CD8⁺ T cells were reduced to the level of healthy nonimmunized mice. (B) Expression of E-selectin, P-selectin, RANTES (CCL5), and CXCL1 was quantified in the brain by qPCR in a separate experiment (n = 5-8/group). (C) Total splenocytes from C57BL/6 (H-2^b) mice (800.000 cells/200 μl) were cultured for 24 or 48 hours with various cytokines (all 10 ng/ml). CCL5 was measured in the supernatant by ELISA. (D) Total splenocytes (Total) or splenocytes depleted of CD11b⁺ cells (11b^–) Ly6C⁺ cells (Ly6C^–) or CCR2⁺ cells (CCR2^–) (500.000 cells/200 μl) were cultured for 24 hours with IL-3 (10 ng/ml). CCL5 was measured in the supernatant by ELISA. One out of 2 representative experiments is shown. Data are represented as mean ±SEM, one-way ANOVA test of anti–IL-3 or no EAE vs. Control: *P ≤ 0.05, **P < 0.01, ***P < 0.001.