Mobilization of leukocytes in patients with severe sepsis and septic shock is associated with increased apoptosis, as detected by Annexin V binding

Methods: Over a 6 month period, 33 patients with severe sepsis or septic shock were studied in the intensive care unit. Annexin V binding by leukocytes was determined daily using flow cytometry and FITC-labeled Annexin V. Transient leukocytosis, or peaks in leukocyte counts, were defined as individual increase of at least 30% within 2 days, followed by a decrease of at least 30% within the following 2 days. Results: Nine, 14 and 10 peaks in neutrophil, monocyte and lymphocyte counts, respectively, were observed in 6, 9 and 10 patients; in all of these patients, increased Annexin V binding by neutrophils, monocytes and lymphocytes, respectively, by 69% up to 809% (median 215%), by 32% up to 973% (median 330%), and by 32% up to 4713% (median 224%), respectively, paralleled the neutrophil, monocyte and lymphocyte (in 13/14 episodes) peaks, respectively. During periods in which neutrophil, monocyte and lymphocyte numbers were stable, Annexin V binding was constant as well.