Figure 1

The clinical correlation of activated protein C-induced MPs with survival, EPCR expression and anticoagulant properties. Figure 1 shows the effect of rhAPC treatment on (A) CD13+ MPs, and (B) APC levels on MPs. MPs from 50 septic patients obtained on Day 1 (25 treated with rhAPC and 25 matching untreated non-rhAPC patients) were analysed by flow cytometry for CD13 positive MPs/ml of plasma. MPs were stained with PE IgG control or CD13 antibodies. Levels of APC on the MPs were quantified using S2366 by ELISA on MPs isolated from rhAPC-treated or non-treated patients. Survival at 28 days is denoted by + (n = 16 for both treated and untreated groups) and death by - (n = 9 for both groups). ** indicates significance of P ≤0.016 by Mann-Whitney U test with Bonferroni correction. (C) Levels of EPCR expression were measured by ELISA on MPs isolated from plasma and the residual MP-free plasma from six rhAPC treated patients (light bars) and six matching untreated patients (dark bars) obtained on Day 0 and Day 1 (of rhAPC treatment or controlled time-point in non-rhAPC group). **P < 0.05 indicates significance difference between pre- vs. during-rhAPC as assessed by a Mann-Whitney U test. (D) APC activity on MP from six patients on Days 1 and 4 was estimated by the ability to generate thrombin after a prior Factor Va incubation step. The MPs were also incubated with Protein C antibody (PCAb) and α₁-antitrypsin (α₁AT) for assessing APC specificity, with APC plus phospholipid vesicles (APC + PCPS) as positive control and APC plus soluble endothelial protein C receptor (sEPCR) as negative control. The mean values ± SD are from duplicate samples in three experiments from each patient. *P < 0.05 and **P < 0.005 indicates significant comparisons between Day 0 vs. Day 1, Day 0 vs. Day 4 in the absence and presence of PC antagonists.