Neutrophils from critically ill patients show similarities to healthy neutrophils that have been exposed to rhC5a. (A) RhoA activation in response to zymosan is impaired in patient neutrophils. **P = .002 by Mann-Whitney U test. Data are shown as median and interquartile range (n = 20: 10 patients and 10 healthy volunteers). (B) Actin polymerization following 5 minutes of zymosan exposure is impaired in patients. **P = .006 by t test. Data are shown as mean and SEM (n = 15: 10 patients and 5 healthy volunteers). (C) Representative histograms illustrating the shift in geometric mean fluorescence before (red) and after (blue) exposure of cells to zymosan; note the contrast with Figure 2B. (D) GM-CSF restores phagocytosis in patients' neutrophils. ***P < .001 by Wilcoxon rank sum test. Solid lines indicate median values (n = 24 patients).