Blocking IL-10 signaling alters macrophage polarization and promotes inflammatory functions. (A) Heatmap representing differentially expressed genes (P_adj ≤ 0.05, fold change ≥2) in the lungs of IgG control versus αIL-10R–treated memory mice, which were challenged with influenza and sampled at 2 dpi; gene expression is shown relative to lungs of uninfected memory mice (Uninf.). Each column represents the averaged expression compiled from biological replicates (n = 3–4 mice) for each condition and time point. Gene expression is row-normalized. Statistical significance was determined by the Wald test using DeSeq2. (B) Arg1⁺ expression in lung macrophages from control- or αIL-10R–treated mice at indicated times after infection shown in representative flow cytometry plots (left, 5 dpi) and compiled results from individual mice (right). (C and D) CCL24 levels and (D) other macrophage-derived cytokine levels in the BAL fluid of control or αIL-10R–treated mice undergoing secondary infection. (E) Lung macrophage content in control- or αIL-10R–treated mice from 2 to 5 dpi. (F) Expression of inflammatory phenotypic markers by lung macrophages at indicated times after infection shown in representative histograms at 4 dpi (left) and graphs of compiled kinetic data (right). Data in B–F are representative of two independent experiments (n = 9 mice/group); points represent mean values, and error bars indicate standard deviation. Statistical significance was determined by two-way ANOVA. ****P ≤ 0.0001; ***P ≤ 0.001; **P ≤ 0.01; *P ≤ 0.05.