Fig. 1

Inhibiting complement over-activation demonstrates therapeutic efficacy in H1N1A/MRSA co-infected mice. a Schematic illustration of developing H1N1A/MRSA co-infected mouse model and treatment strategies. b UMAP plot of 196,918 cells from mice treated with PBS, MRSA, PR8, and coinfection for 24 h/72 h/120 h. c Differential interaction strength of significant ligand-receptor pairs for all cell clusters. d Top pathways from GSEA of T cells. e UMAP plot of seven subsets of macrophages colored by cluster identification. f Ratio of all cells belonging to the macrophages clusters. g Bubble plot showing the expression of functional pathways of macrophages in different groups. Immunohistochemistry of lung tissues was performed to detect the accumulation of complement (h) C3d and (i) C5 in co-infected mice with different treatments over time. The scale bar represents 200 μm. Histogram of the percentage of (j) C3d and (k) C5 positive area. N = 3/group. The survival curve of (l) C3 knock-out (C3^−/−), (m) C5 knock-out (C5^−/−). n Hematoxylin and eosin (H&E) staining in representative mouse lung sections among knock-out groups (d-2 coinfection, C3^−/− and C5^−/− treated groups). o Quantification of serum IFN-γ, TNF-α, IL-6 and IL-8 levels by ELISA. N = 4/group. The survival curve of (p) CVF treated and (q) anti-C5aR treated mice. r H&E staining in representative mouse lung sections among therapy groups (d-2 coinfection, CVF treated and anti-C5aR treated groups). s Quantification of serum IFN-γ, TNF-α, IL-6 and IL-8 levels by ELISA. N = 4/group. All quantitative results were presented as mean ± SD. Type Il pneumocyte, T2P, inflammatory pneumocyte, IP; type I pneumocyte, T1P; lfitm3+ pneumocyte, lfitm3+P; B-cell-stimulating pneumocyte, BP. All the experimental groups in (g, h) were compared by a two-way ANOVA followed by Bonferroni’s multiple comparisons test; p < 0.05 indicates a significant difference. Ns, p > 0.05; *p < 0.05; **p < 0.01; ***p < 0.001; ****p < 0.0001. All the experimental groups in (n) and (p) were compared by a one-way ANOVA followed by Benjamini and Hochberg multiple comparisons test; p < 0.05 indicates a significant difference. Ns, p > 0.05; *p < 0.05; **p < 0.01; ***p < 0.001; ****p < 0.0001