(A) Levels of IL-6, IL-8, and TNF-α from bulk human PBMCs treated with LPS and the indicated IL-10 variant, measured by ELISA. (mean ± SEM, n=3, N=3, **P<0.01, two-sided Student’s t test; ND, not detectable). (B) Levels of IFN-γ from bulk PBMCs stimulated with anti-CD3 antibody for 72 hours, alone or in combination with the indicated IL-10 variants, measured by ELISA. (mean ± SEM, n=3, N=3, **P<0.01, two-sided Student’s t test). (C) Representative histograms of MHC class II surface expression on human peripheral monocytes activated with LPS alone or in combination with the indicated IL-10 variant, analyzed by flow cytometry (n=5, N=2). (D) Levels of IL-6, IL-8, and TNF-α produced by primary human monocyte-derived macrophages stimulated with LPS, measured by ELISA. (mean ± SEM, n=3, N=3, **P<0.01, two-sided Student’s t test). (E) Survival after intraperitoneal injection of LPS (15 mg/kg) in combination with PBS, WT IL-10 or 10-DE (n=8 mice, N=2, **P <0.01, log-rank Mantel-Cox test). (H, I) Levels of TNF-α, IL-6, and haptoglobin in mouse serum following injection of LPS (4 mg/kg) and the indicated IL-10 variant, measured by ELISA (mean ± SEM, n=3, N=2, *P<0.05. **P<0.01, two-sided Student’s t test).