IL-1 KO mice do not exhibit increased expression of the alternative activation marker, Ym1, after SCI. (A) Expression of the marker for alternatively activated microglia/macrophage, Ym1, was semi-quantified by immunoblotting. Ym1 levels in the wild-type mice (n = 6 to 7, open column) were increased on the 7th and 14th dpo. However, the level of Ym1 in the IL-1KO mice (n = 5 to 6, filled column) is significantly lower than that for the wild-type mice. Data are expressed as mean ± SE. *: P <0.05 (Student's t-test). (B) Immunostaining at the 14th dpo for Ym1 in the spinal cord after injury. The immunoreactivity of Ym1 (red) is observed around the lesion epicenter (epi) and is more intense in the wild-type than in IL-1 KO mice. (C) Ym1 immunoreactivity (red) merges with F4/80 immunoreactivity (green, microglia/macrophage marker) in both groups of animals. (D) Moreover, Ym1 (blue) co-localizes with cells that are immunopositive for F4/80 (green) and IGF-1 (red) in both groups. Dpo, days post-operatively; SCI, spinal cord injury.