Expression of NK Cell and Monocyte Receptors in Critically Ill Patients – Potential Biomarkers of Sepsis

Sepsis is characterized by activation of both the innate and adaptive immune systems as a response to infection. During sepsis, the expression of surface receptors expressed on immune competent cells, such as NKG2D and NKp30 on NK cells and TLR4 and CD14 on monocytes, is partly regulated by pro‐ and anti‐inflammatory mediators. In this observational study, we aimed to explore whether the expression of these receptors could be used as diagnostic and/or prognostic biomarkers in sepsis. Patients with severe sepsis or septic shock (n = 21) were compared with critically ill non‐septic patients (n = 15). Healthy volunteers (n = 15) served as controls. To elucidate variations over time, all patients were followed for 4 days. Cell surface expression of NKG2D, NKp30, TLR4 and CD14 and serum levels of IL‐1β, IL‐6, IFN‐γ, TNF‐α, IL‐4 and IL‐10 was estimated by flow cytometry. We found that NK cell expression of NKG2D and monocyte expression of CD14 were lower in the septic patients compared with the non‐septic patients, both at ICU admission and during the observation period (P < 0.01 for all comparisons). Both at ICU admission, and during the observation period, levels of IL‐6 and IL‐10 were higher in the septic patients compared with the non‐septic patients (P < 0.001 for all comparisons). Conclusion: As both NKG2D and CD14 levels appear to distinguish between septic and non‐septic patients, both NKG2D and CD14 may be considered potential diagnostic biomarkers of severe sepsis and septic shock.