Sepsis Patients Display a Reduced Capacity to Activate Nuclear Factor-κB in Multiple Cell Types.

OBJECTIVES: Sepsis is a complex clinical condition associated with high morbidity and mortality. A distinctive feature of sepsis is the reduced capacity of leukocytes to release proinflammatory cytokines in response to ex vivo stimulation. Cellular signaling events leading to immunosuppression in sepsis are not well defined. We investigated cell-specific signaling events underlying the immunosuppressed phenotype in sepsis. DESIGN: Ex vivo study. SETTING: ICU of an academic hospital. PATIENTS: Nineteen patients with sepsis and 19 age-matched healthy controls. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: The phosphorylation state of p38 mitogen activated protein kinase and nuclear factor kappa-light-chain-enhancer of activated B cells were determined in ex vivo stimulated CD4 T cells, CD8 T cells, B cells, monocytes, and neutrophils. Messenger RNA expression levels of p38 mitogen activated protein kinase and nuclear factor kappa-light-chain-enhancer of activated B cells and negative regulators tumor necrosis factor-α-induced protein 3 (A20) and mitogen activated protein kinase phosphatase-1 were determined in neutrophils and peripheral blood mononuclear cells. Upon ex vivo stimulation, monocytes of sepsis patients were less capable in phosphorylating nuclear factor kappa-light-chain-enhancer of activated B cells. Sepsis was also associated with reduced phosphorylation of nuclear factor kappa-light-chain-enhancer of activated B cells in stimulated B cells, CD4 and CD8 T cells. Messenger RNA expression levels of nuclear factor kappa-light-chain-enhancer of activated B cells and A20 were diminished in peripheral blood mononuclear cells of sepsis patients, whereas p38 mitogen activated protein kinase messenger RNA was up-regulated. In neutrophils of sepsis patients, mitogen activated protein kinase phosphatase-1 messenger RNA levels were down-regulated. CONCLUSIONS: Sepsis-induced immunosuppression associates with a defect in the capacity to phosphorylate nuclear factor kappa-light-chain-enhancer of activated B cells in lymphoid cells and monocytes.

Plasma fractalkine is a sustained marker of disease severity and outcome in sepsis patients.

INTRODUCTION: Fractalkine is a chemokine implicated as a mediator in a variety of inflammatory conditions. Knowledge of fractalkine release in patients presenting with infection to the Intensive Care Unit (ICU) is highly limited. The primary objective of this study was to establish whether plasma fractalkine levels are elevated in sepsis and associate with outcome. The secondary objective was to determine whether fractalkine can assist in the diagnosis of infection upon ICU admission. METHODS: Fractalkine was measured in 1103 consecutive sepsis patients (including 271 patients with community-acquired pneumonia (CAP)) upon ICU admission and at days 2 and 4 thereafter; in 73 ICU patients treated for suspected CAP in whom this diagnosis was refuted in retrospect; and in 5 healthy humans intravenously injected with endotoxin. RESULTS: Compared to healthy volunteers, sepsis patients had strongly elevated fractalkine levels. Fractalkine levels increased with the number of organs failing, were higher in patients presenting with shock, but did not vary by site of infection. Non-survivors had sustained elevated fractalkine levels when compared to survivors. Fractalkine was equally elevated in CAP patients and patients treated for CAP but in whom the diagnosis was retrospectively refuted. Fractalkine release induced by intravenous endotoxin followed highly similar kinetics as the endothelial cell marker E-selectin. CONCLUSIONS: Plasma fractalkine is an endothelial cell derived biomarker that, while not specific for infection, correlates with disease severity in sepsis patients admitted to the ICU.

Reduced Responsiveness of Blood Leukocytes to Lipopolysaccharide Does not Predict Nosocomial Infections in Critically Ill Patients.

Critically ill patients show signs of immune suppression, which is considered to increase vulnerability to nosocomial infections. Whole-blood stimulation is frequently used to test the function of the innate immune system. We here assessed the association between whole-blood leukocyte responsiveness to lipopolysaccharide (LPS) and subsequent occurrence of nosocomial infections in critically ill patients admitted to the intensive care unit (ICU). All consecutive critically ill patients admitted to the ICU between April 2012 and June 2013 with two or more systemic inflammatory response syndrome criteria and an expected length of ICU stay of more than 24 h were enrolled. Age- and sex-matched healthy individuals were included as controls. Blood was drawn the first morning after ICU admission and stimulated ex vivo with 100 ng/mL ultrapure LPS for 3 h. Tumor necrosis factor-α, interleukin-1ß (IL-1ß), and IL-6 were measured in supernatants. Seventy-three critically ill patients were included, of whom 10 developed an ICU-acquired infection. Compared with healthy subjects, whole-blood leukocytes of patients were less responsive to ex vivo stimulation with LPS, as reflected by strongly reduced tumor necrosis factor-α, IL-1ß, and IL-6 levels in culture supernatants. Results were not different between patients who did and those who did not develop an ICU-acquired infection. The extent of reduced LPS responsiveness of blood leukocytes in critically ill patients on the first day after ICU admission does not relate to the subsequent development of ICU-acquired infections. These results argue against the use of whole-blood stimulation as a functional test applied early after ICU admission to predict nosocomial infection.