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Open Access Research

Early apoptosis of blood monocytes in the septic host: is it a mechanism of protection in the event of septic shock?

Evangelos J Giamarellos-Bourboulis1*, Christina Routsi2, Diamantis Plachouras1, Vassiliki Markaki2, Maria Raftogiannis1, Dimitrios Zervakis2, Vassilios Koussoulas1, Stylianos Orfanos3, Anastasia Kotanidou2, Apostolos Armaganidis3, Charis Roussos2 and Helen Giamarellou1

Author Affiliations

1 4th Department of Internal Medicine, University of Athens, Medical School, Greece

2 1st Department of Critical Care, University of Athens, Medical School, Greece

3 2nd Department of Critical Care, University of Athens, Medical School, Greece

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Critical Care 2006, 10:R76  doi:10.1186/cc4921


See related commentary by Moraes and Downey, http://ccforum.com/content/10/3/146

Published: 12 May 2006

Abstract

Introduction

Based on the central role of the triggering of monocytes for the initiation of the septic cascade, it was investigated whether apoptosis of blood monocytes in septic patients is connected to their final outcome.

Methods

Blood monocytes were isolated from 90 patients with septic syndrome due to ventilator-associated pneumonia on days 1, 3, 5 and 7 from the initiation of symptoms. Apoptosis was defined after incubation with annexin-V-fluorescein isothiocyanate and propidium iodine and reading by a flow cytometer. The function of first-day monocytes was evaluated from the concentrations of tumour necrosis factor alpha (TNFα) and IL-6 in supernatants of cell cultures after triggering with endotoxins. TNFα, IL-6 and IL-8 were estimated in serum by an enzyme immunoassay.

Results

Mortality rates of patients with apoptosis ≤50% compared with patients with apoptosis >50% were 49.12% and 15.15%, respectively (P < 0.0001). Kaplan-Meier analysis showed a 28-day survival benefit in patients with septic shock and monocyte apoptosis >50% compared with those patients with apoptosis ≤50% (P = 0.0032). Production of IL-6 by monocytes on the first day by patients with apoptosis ≤50% was similar compared with monocytes isolated from healthy controls. Serum concentrations of TNFα were higher in patients with monocyte apoptosis ≤50% and septic shock compared with patients with apoptosis >50% on day 7; similar findings occurred for serum IL-6 on days 1 and 7 and for serum IL-8 on days 1 and 5.

Conclusion

Early apoptosis of monocytes upon presentation of clinical signs of sepsis is connected to a favourable outcome. These findings are of particular importance for the patient with septic shock, where they might constitute a mechanism of pathogenesis.