Activation of adult primary microglial cells in wild-type and IL-1 KO mice. (A) Primary microglial cells were obtained from young adult wild-type mice. The cells stain with the microglial marker CD11b, but not with the neuronal and astroglial markers, NeuN and GFAP, respectively. A few cells are stained with the oligodendroglial cell marker, MBP. NC (inset) is the primary antibody-free negative control. The microglial cells (n = 3 each group) were stimulated for 24 hours in the presence of the vehicle alone, or supplemented with IFNγ or IL-4 in the presence or absence of IL-1β. Total NO (NOx; B), TNFα (C), arginase specific activity (Arg-1 spe. act.; D) and IGF-1 (E) were determined from the media or cell suspensions. (B) NOx levels increase upon exposure of the cells to IL-1β and in a synergistic manner upon co-treatment of cells with IL-1β and IFNγ, but not when the cotreatment is with IL-4. (C) TNFα levels increase upon exposure of the cells to IFNγ, and further upon co-treatment with IL-1β. Surprisingly, the co-treatment of the cells with IL-4 and IL-1β induced the highest TNFα level among the experimental treatments used. (D) Arg1-specific activity increased significantly upon exposure to IL-4 and further increased when IL-4 and IL-1β were employed together. (E) IGF-1 levels decreased with exposure of the cells to IFNγ and increased in response to IL-4. The response was partially inhibited by cotreatment of the cells with IL-1β. Data are expressed as mean ± SD (n = 3). *: P < 0.05, **: P < 0.01, ***: P < 0.001 compared with the vehicle-treated group in each genotype (one-way ANOVA followed by Dunnett post-hoc test). ANOVA, analysis of variance; IGF-1, insulin-like growth factor.