Fig. 5

Association between interleukin (IL)-6 serum activity and angiopoietin (ANG)2 levels. a Serum was sampled from patients being scheduled for elective on-pump coronary artery bypass graft (CABG) before surgery (preop) and 1, 6 and 24 h after closure of the aortic clamp. Serum was analyzed for IL-6 (enzyme-linked immunosorbent assay (ELISA)) (left). The early increase in IL-6 1 h after CABG correlates with further increasing ANG2 levels measured 24 h after de-clamping (right): n = 28 (24 h time point, n = 26), median with percentile 25–75, ***p <0.001 (vs. preop). b Human pulmonary microvascular endothelial cells were cultured in 96-well plates and pre-incubated with filtered and diluted (5 %) patient serum (preop (clear bars) or 1 h (hatched bars), respectively) and anti-human-IL-6 antibody (1 μg/ml) for 24 h. Supernatant was discarded, and triggered ANG2 secretion was induced by adding thrombin (1 IU/ml) in fresh culture medium. After 1 h, the ANG2 concentration was determined by ELISA. Fold change of triggered ANG2 secretion (compared to basal secretion without thrombin addition) is shown after pre-incubation with serum with low IL-6 activity (white bars) vs. serum with high IL-6 concentration (gray bars). The bar on the right shows ANG2 secretion when ‘high IL-6 1 h’ serum pre-incubation was combined with anti-human-IL-6 antibody: n = 6–9, mean ± standard error of the mean, *p <0.05. CPB cardiopulmonary bypass