Polymorphonuclear Neutrophil-Derived Ectosomes Interfere with the Maturation of Monocyte-Derived Dendritic Cells

Abstract

Polymorphonuclear neutrophils (PMNs) are a key component of the innate immune system. Their activation leads to the release of potent antimicrobial agents through degranulation. Simultaneously, PMNs release cell surface-derived microvesicles, so-called ectosomes (PMN-Ect). PMN-Ect are rightside-out vesicles with a diameter of 50–200 nm. They expose phosphatidylserine in the outer leaflet of their membrane and down-modulate monocyte/macrophage-activation in vitro. In this study, we analyzed the effects of PMN-Ect on maturation of human monocyte-derived dendritic cells (MoDCs). Intriguingly, exposing immature MoDCs to PMN-Ect modified their morphology, reduced their phagocytic activity, and increased the release of TGF-β1. When immature MoDCs were incubated with PMN-Ect and stimulated with the TLR4 ligand LPS, the maturation process was partially inhibited as evidenced by reduced expression of cell surface markers (CD40, CD80, CD83, CD86, and HLA-DP DQ DR), inhibition of cytokine-release (IL-8, IL-10, IL-12, and TNF-α), and a reduced capacity to induce T cell proliferation. Together these data provide evidence that PMN-Ect have the ability to modify MoDC maturation and function. PMN-Ect may thus represent an as yet unidentified host-factor influencing MoDC maturation at the site of injury, thereby possibly impacting on downstream MoDC-dependent immunity.

Changing world of neutrophils

“…Further, they demonstrated that PMN-derived EVs increased the secretion of the anti-inflammatory cytokine TGF-β1 from monocytes, whereas the stimulated release of IL-8, IL-10 and TNFα was decreased [40]. Secretion of TGF-β1 was induced also in monocyte-derived dendritic cells, where incubation with PMN-EVs interfered with the LPS-induced differentiation process indicated by a decrease of release of inflammatory cytokines, decrease of phagocytosis and T-cell stimulation [34]. The inhibitory effects were initiated by membrane components of PMN-EVs which led to the activation of the Mer tyrosine kinase pathway in monocytes, resulting eventually in inhibition of transcription factor NF-κB and downregulation of several pro-inflammatory genes [35].…”

“…Most of the data on PMN-derived EVs (called in these studies ectosomes) come from the laboratory of Dr. Schifferli [26,[34][35][36]39,40,45,[93][94][95][96]. They characterized the size and surface properties of EVs released upon fMLP-stimulation and came to the conclusion that both the in vitro and the in vivo generated EVs are right-side out [39,45].…”

Exosomes as intercellular signalosomes and pharmacological effectors

“…Exosomes bear specific protein markers such as tetraspanins (CD63,CD9,CD81), HeatShock proteins (HSP 70) or the Transferin Receptor in the case of reticulocyte (TfR), that make the exosomes distincts from vesicles released upon plasma membrane shedding and called ectosomes [3]. These latter contain distinct markers such as glycophorin.…”

Cell-Cell Communication Via Extracellular Membrane Vesicles and Its Role in the Immune Response

“…PS present in the outer surface of ectosomes is found to be responsible for the immunomodulatory property of ectosomes (Gasser and Schifferli, 2004), and a specific receptor protein tyrosine kinase (i.e., Mer receptor tyrosine kinase) is involved in the intracellular signaling process (Scott et al, 2001). PMN-derived ectosomes also have an inhibitory effect on immature DCs (Eken et al, 2008;Gasser and Schifferli, 2004). Thus, when immature DCs are cultured with LPS in the presence of PMN-derived ectosomes, expression levels of the cytokines and costimulatory and adhesion ligands required for T cell activation are significantly reduced, compromising T cell activation.…”