Lipopolysaccharide—cell interaction and induced cellular activation in whole blood of septic patients

Abstract

We used biotinylated LPS (LPSb) and flow cytometry to study LPS-monocyte interaction and LPS-induced cellular activation in whole blood from septic patients (SP). Expression of surface activation markers was evaluated on monocytes (HLA-DR) and T lymphocytes (CD69 and CD95), and intracellular TNF-alpha on monocytes. Saturating curve and kinetics of LPSb detection on monocytes were similar in SP and healthy volunteers (HV). LPSb bound to monocytes was detected after 5 min of incubation in both groups, with a more pronounced decay in SP. Monocytes from SP had a lower expression of HLA-DR as compared to HV, both constitutive and upon LPS stimulation. The proportion of monocytes producing TNF-alpha after LPS stimulus was higher in HV than SP (mean +/- SD = 25.2 +/- 14.2% and 2.2 +/- 2.6%, respectively, P < 0.001). LPS-induced CD69 on T CD8+ and CD8- lymphocytes was similar for patients and controls. Expression of CD95 on T lymphocytes was higher in SP as compared to HV on T CD8+ cells (GMFI, mean +/- SD = 22.3 +/- 14.6 and 8.6 +/- 5.0, respectively, P = 0.01) and CD8- cells (GMFI, mean +/- SD = 28.3 +/- 7.7 and 14 +/- 4.3 respectively, P < 0.001). Thus, monocytes and lymphocytes seem to respond differently to LPS in septic patients. Monocyte hyporesponsiveness appears not to be related to a decreased binding capacity of LPS, but rather to an impaired signal transduction.

Differential expression of toll-like receptor signaling cascades in LPS-tolerant human peripheral blood mononuclear cells

“…CD180 (RP105) and its adaptor LY86 (MD-1), proteins mediating inhibition of TLR4 signaling that are present on the surface of B-cells (Divanovic et al 2005), were inhibited under both conditions, Medium-LPS and LPS-LPS. These findings are in agreement with previous findings in cells from septic patients, both at level of gene expression (Salomao et al 2009) and surface HLA-DR protein expression (Salomao et al 2002).…”

“…In addition, we also reported that LPS-induced production of TNF-␣ was lower in supernatants of PBMC from septic patients than those from healthy volunteers, while no difference was found in IL-10 levels (Rigato and Salomao 2003). Despite the preservation of the ability of LPS to bind the cell surface, the response of monocytes to LPS was decreased (Salomao et al 2002).…”

Upregulation of Reactive Oxygen Species Generation and Phagocytosis, and Increased Apoptosis in Human Neutrophils During Severe Sepsis and Septic Shock

“…This upregulation contrasts with the hyporesponse reported for monocytes, where decreased TNF-␣ production and HLA-DR expression upon LPS stimulation have been reported (22)(23)(24).…”

“…We have previously demonstrated that the expression of CD95 or Fas is higher on T lymphocytes from patients with sepsis compared with healthy volunteers (23). This upregulation has been recently verified in patients with systemic inflammatory response syndrome (SIRS), with multiple organ dysfunction syndrome (MODS), or likely to develop the syndrome (28).…”

Increased Percentages of T Helper Cells Producing IL-17 and Monocytes Expressing Markers of Alternative Activation in Patients with Sepsis

“…It has been suggested that a state of hyporesponse or immune paralysis follows the initial inflammatory response in humans and experimental sepsis, which is related to susceptibility to nosocomial infections and late lethality [2]–[5].…”