Increased monocyte activation and tissue factor expression in patients with sepsis

Background

Tissue factor (TF) is believed to play an important role in the initiation of intravascular coagulation. Accumulating evidence has been provided that TF expression in monocytes may determine disturbances in intravascular coagulation and outcome in sepsis. A direct proof of an increased monocyte TF activity and/or antigen in septic patients is still lacking.

Patients and methods

47 patients treated in the Intensive Care Unit of an university hospital were included in the study. Sepsis and the degree of organ dysfunction were assessed according to the criteria of the ACCP/SCCM Consensus Conference and the SOFA score. Blood samples from an arterial catheter were anticoagulated with sodium citrate. Binding to monocytes of FITC-labelled monoclonal antibodies against TF and CD11b was determined by flowcytometry.

Results

Compared to non-septic patients (n = 20) monocytes of septic patients (n = 27) bound significantly higher amounts of anti- TF antibody (mean fluorescence intensity - MFI: 14.3 ± 3.3 vs. 18.9 ± 6.4; P < 0.01). The same was true for binding of the antibody against the activation-dependent antigen CD11b. MFI in non-septic patients amounted to 266 ± 72 and in septic patients 335 ± 86 (P < 0.005). Using a non-parametric analysis we found significant correlation between anti-TF and anti-CD11b binding (P < 0.03) as well as between SOFA Score and anti-CD11b or anti-TF binding (P < 0.03 and 0.02, respectively).

Conclusion

The results indicate that monocytes in septic patients are on a higher activation level and have higher amounts of TF antigen when compared to non-septic ICU patients. Thus, the study confirmed the proposed role of monocyte TF expression for sepsis-associated activation of coagulation.