Functional Ex Vivo Testing of Alveolar Monocytes in Patients with Pneumonia-Related ARDS.

Inès Bendib,Véronique Godot,Sophie Hüe,Asma Beldi-Ferchiou,Guillaume Carteaux,Jean-Daniel Lelièvre,Keyvan Razazi,Nicolas De Prost,Mathieu Surenaud,Bernard Maitre,Frédéric Schlemmer,Armand Mekontso Dessap,Yves Lévy

doi:10.3390/cells10123546

Abstract

Biomarkers of disease severity might help with individualizing the management of patients with acute respiratory distress syndrome (ARDS). During sepsis, a sustained decreased expression of the antigen-presenting molecule human leucocyte antigen-DR (HLA-DR) on circulating monocytes is used as a surrogate marker of immune failure. This study aimed at assessing whether HLA-DR expression on alveolar monocytes in the setting of a severe lung infection is associated with their functional alterations. BAL fluid and blood from immunocompetent patients with pneumonia-related ARDS admitted between 2016 and 2018 were isolated in a prospective monocentric study. Alveolar and blood monocytes were immunophenotyped using flow cytometry. Functional tests were performed on alveolar and blood monocytes after in vitro lipopolysaccharide (LPS) stimulation. Phagocytosis activity and intracellular tumor necrosis factor (TNF) production were quantified using fluorochrome-conjugated-specific antibodies. Ten ARDS and seven non-ARDS control patients were included. Patients with pneumonia-related ARDS exhibited significantly lower HLA-DR expression both on circulating (p < 0.0001) and alveolar (p = 0.0002) monocytes. There was no statistically significant difference observed between patient groups (ARDS vs. non-ARDS) regarding both alveolar and blood monocytes phagocytosis activity. After LPS stimulation, alveolar (p = 0.027) and blood (p = 0.005) monocytes from pneumonia-related ARDS patients had a significantly lower intracellular TNF expression than non-ARDS patients. Monocytes from pneumonia-related ARDS patients have a deactivated status and an impaired TNF production capacity but display potent phagocytic activity. HLA-DR level expression should not be used as a surrogate marker of the phagocytic activity or the TNF production capacity of alveolar monocytes.

Highlights

Pulmonary infections account for the vast majority of acute respiratory distress syndrome (ARDS) risk factors [1] and are associated with septic shock in about 70% of cases [2]
In the current study, which is an ancillary study of the PICARD study [6], we aimed to assess, in a prospective cohort of patients with moderate to severe pneumonia-related ARDS: (1) the phenotype of alveolar and blood monocytes and compare it to those of non ARDS patients; (2) the function of alveolar and blood monocytes; and (3) explore alveolar monocytes functions according to their level of human leucocyte antigen-DR (HLA-DR) expression
The main results of the current study are as follows: (1) Alveolar monocytes from ARDS patients showed a decreased HLA-DR expression, as compared with blood monocytes, and a significant correlation with cytokines involved in the activation of innate immunity, as well as with markers of alveolar epithelial/endothelial injury; alveolar monocytes of ARDS patients, together with those of controls, showed higher programmed cell death receptor ligand-1 (PD-L1) expression than those of blood monocytes; (2) The phagocytosis activity and intracellular production of tumor necrosis factor (TNF) after ex vivo LPS stimulation of alveolar monocytes were decreased in ARDS patients; and (3) Alveolar monocytes phagocytosis capacity and LPS-induced intracellular TNF concentrations did not differ according to their HLA-DR− vs. HLA-DR+ phenotype

Summary

Introduction

Pulmonary infections account for the vast majority of acute respiratory distress syndrome (ARDS) risk factors [1] and are associated with septic shock in about 70% of cases [2]. A sustained decreased expression of the antigen presenting molecule human leucocyte antigen-DR (HLA-DR) on circulating monocytes is used as a surrogate marker of immune failure and higher risk of death [7,8,9]. The overexpression of programmed cell death receptor ligand-1 (PD-L1) occurs during sepsis and correlates with higher mortality [10]. Monocyte deactivation reflected by down regulation of HLA-DR expression on circulating monocytes [11,12] has been associated with the phenomenon of endotoxin tolerance, defined by a reduction of TNF secretion capacity after ex vivo lipopolysaccharide (LPS) stimulation [13]. Routine assays provide only measurements of immune cell surface biomarkers [14,15]

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