Mechanisms for the diminished neutrophil exudation to secondary inflammatory sites in infected patients with a systemic inflammatory response (sepsis)

Abstract

Septic patients deliver fewer PMNs to secondary inflammatory sites. In addition, neutrophil exudation results in loss of the small priming effect for phagocytosis and bactericidal function induced by sepsis. Failure to produce a gradient to C5a and intravascular shedding of L-selectin may be responsible for this sepsis-induced reduction in neutrophil exudation to secondary inflammatory sites.

Profound Differences in Leukocyte-Endothelial Cell Responses to Lipopolysaccharide Versus Lipoteichoic Acid

“…Interestingly, this leukocytopenia in wild-type animals translated into fewer leukocyte-endothelial cell interactions in peripheral vasculature and an inability to recruit leukocytes (adhesion and emigration) into peripheral microcirculations, including the peritoneum and skeletal muscle. This delay in leukocyte recruitment into nonpulmonary tissues in septic humans has been appreciated for many years and may account for the multiorgan dysfunction associated with septic shock (49). Although LPS has been shown to increase endothelial adhesion molecule expression in all tissues (32), the preferential recruitment of leukocytes into lungs may not be related to molecular adhesive events, but rather due to physical trapping of activated (rigid) leukocytes within narrow architecture of pulmonary capillaries (3,6,30), which precedes the adhesion molecule expression in other tissues.…”

Alteration of Chemoattractant Receptor Expression Regulates Human Neutrophil Chemotaxis In Vivo

“…However, the C5a gradient is absent in septic patients secondary to elevation in serum C5a. 4 Thus, our data to date suggest a defect in C5a-mediated chemotaxis in sepsis resulting from both a lack of a C5a gradient and a significant loss of C5a receptors and C5a chemotactic response in circulating PMNs. These results provide a mechanism to explain the observed decrease in PMN delivery to skin window blisters in septic patients.…”

“…1,2 Appropriate recruitment of polymorphonuclear neutrophils (PMNs) to a site of inflammation is a principal component of effective host defense against bacterial and fungal infection. 3 We have previously shown that septic patients have reduced delivery of neutrophils to skin blisters, 4,5 and we believe that diminished PMN delivery to remote sites may contribute to sepsis-related immunosuppression, leading to "second-front" infections, subsequent organ dysfunction, and death. Given the essential role of the PMN in both health and disease, our investigations have focused on the regulation of human PMN delivery in vivo.…”

“…Because we have previously shown that neutrophil delivery to skin blister sites is reduced by 72% in septic patients with active infection and the systemic inflammatory response syndrome, 4 we hypothesized that neutrophil chemoattractant receptors and chemotaxis in the circulating PMNs of septic patients would be diminished. In this experiment, we found a significant reduction in C5a receptors on circulating PMNs from septic patients and a corresponding decrease in chemotaxis to C5a.…”

“…In 5-mL tubes, 10 L (1-2 g) immunofluorescent monoclonal antibody was incubated along with 100 L whole blood for 30 minutes at room temperature in the dark. Subsequently, 2 mL monoclonal lysing solution (1 L dH 2 O, 8.26 g NH 4 Cl, 1 g KHCO 3 , 0.037 g Na 2 EDTA) was added to the mixture, and again it was stored in the dark for 10 minutes. After neutrophil sedimentation (400g at 4°C for 5 minutes), cells were washed twice with PBS with 1% fetal bovine serum and 0.1% Azide (Sigma, Oakville, Ontario), and were finally suspended in 2% paraformaldehyde (Fisher, Ontario) and promptly analyzed by flow cytometry.…”