Biology subjects

Huot, S.

Publications and source records attributed to Huot, S..

4 recordsLinked to original sources

bioRxiv2025

Neutrophil Fc gamma RI expression as a determinant of oxidative responses in human blood

Neutrophils express Fc receptors on their surface to trap immune complexes. While the roles of Fc{gamma}RIIa and Fc{gamma}RIIIb have extensively been studied in that context, that of Fc{gamma}RI remains elusive. Recently, aggregated IgGs have been shown to induce rapid Fc{gamma}RI up-regulation and reactive oxygen species (ROS) generation, but the biological relevance of this process is still unclear. In this study, incubation of blood samples from healthy volunteers with heat-aggregated IgGs, used as a model of immune complexes, rapidly up-regulated the surface expression of Fc{gamma}RI, predominantly on neutrophils, as measured by flow cytometry. Stimulation of isolated neutrophils with aggregated IgGs resulted in the production of ROS in an Fc{gamma}RI-dependent fashion, as monitored with a luminol-based chemiluminescence assay. Cytochalasin B potentiated Fc{gamma}RI expression and ROS production. In resting blood, positive correlations between neutrophil Fc{gamma}RI and ROS production were observed, both in healthy volunteers and patients with lupus. This study unveils a potentially central regulatory role for neutrophil Fc{gamma}RI in ROS production, both in healthy individuals and patients with lupus, and identifies neutrophil Fc{gamma}RI as a promising target to modulate oxidative response.

immunology↗

bioRxiv2025

Acquired Neutrophil Dysregulation in Systemic Lupus Erythematosus: A Central Role for Fc gamma Receptor Engagement

PurposeSystemic lupus erythematosus is an autoimmune disease hallmarked by a plethora of autoantibodies, interferon-signature, auto-immune complexes, dysregulation of soluble factors in circulation, and abnormal neutrophils. We characterized the neutrophil phenotype in a cohort of lupus patients and assessed the implication of the cells environment. MethodsBlood samples were analyzed for neutrophil expression of surface markers and viability, by flow cytometry. Neutrophils from healthy volunteers were stimulated with serum samples from lupus patients. Plasma samples were subjected to multiplex analysis. Whole blood and isolated neutrophils were stimulated with lupus-relevant soluble factors or with heat-aggregated IgGs that mimic the engagement of Fc gamma (Fc{gamma}) receptors by immune complexes, for viability and activation analysis. ResultsLupus neutrophils displayed significant alterations in the expression of surface markers of adhesion, complement regulation, degranulation, and immune complex response. They also had reduced viability and increased apoptosis. Stimulation of healthy neutrophils with lupus serum increased apoptosis. Lupus-relevant soluble factors accelerated neutrophil apoptosis. Heat-aggregated IgGs mirrored most of the key alterations in viability and surface marker expression observed in lupus neutrophils. ConclusionThis study offers a prototypical phenotype for neutrophils in lupus, characterized by shortened viability, partial degranulation, heightened adhesion capacity, and responsiveness to complement activation. It also points to Fc{gamma} receptors engagement as a major driver of the phenotype observed herein. Finally, results emphasize the therapeutic potential of targeting neutrophil-immune complex interactions and the inflammatory plasma milieu in lupus, from which neutrophil dysfunction is largely acquired. HIGHLIGHTSO_LINeutrophils from patients with lupus exhibit abnormal phenotype and viability. C_LIO_LIAnalysis of plasmas in lupus reveals altered levels of analytes. C_LIO_LIStimulation of healthy whole blood with a model of immune complexes reproduces most of the neutrophil phenotypic abnormalities observed in lupus. C_LIO_LINeutrophil abnormalities in lupus are largely acquired, rather than representing subsets. C_LI GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=73 SRC="FIGDIR/small/653336v2_ufig1.gif" ALT="Figure 1"> View larger version (17K): org.highwire.dtl.DTLVardef@18547c1org.highwire.dtl.DTLVardef@129f495org.highwire.dtl.DTLVardef@178a36corg.highwire.dtl.DTLVardef@131158b_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗

bioRxiv2025

No Evidence of Direct Activation of Human Neutrophil Responses by Multivalent Prefusion Trimeric SARS-CoV-2 Spike Protein ex vivo

The SARS-CoV-2 Spike (S) protein is essential for viral entry and serves as the primary immunogen in most COVID-19 vaccines. While its role in adaptive immunity is well defined, its potential to contribute directly to innate immune activation and remains incompletely understood. Neutrophils, in particular, are prominent effectors in COVID-19 severity, yet how they respond directly to the S protein presented in a multivalent format is unclear. Here, we investigated whether the S protein can directly activate human neutrophils ex vivo using two biologically relevant models: nanoparticles displaying multivalent stabilized prefusion trimeric S glycoprotein, and purified {beta}-propiolactone-inactivated SARS-CoV-2 virions. Neutrophils were exposed to nanoparticles or inactivated virus, either alone or pre-coated with monoclonal or polyclonal anti-S antibodies. Nanoparticles displaying Respiratory Syncytial Virus (RSV) Fusion (F) protein and purified {beta}-propiolactone-inactivated RSV served as comparators. Across all models and conditions tested, the S protein did not induce significant neutrophil responses. No consistent effects were observed on cell viability, surface marker expression, reactive oxygen species production, neutrophil extracellular trap formation, cytokine release, or inflammatory gene expression--even in the presence of anti-S antibodies mimicking immune complexes. Results with F-nanoparticles and inactivated RSV were similarly modest. These findings indicate that the trimeric prefusion S protein, whether displayed multivalently on nanoparticles or in the context of inactivated viral particles, is insufficient to trigger robust neutrophil activation. This work provides insight into the innate immune profile of the S protein and suggests that its use in vaccine platforms is unlikely to directly provoke neutrophil-mediated inflammatory responses.

immunology↗

bioRxiv2020

IgG-aggregates rapidly up-regulate FcgRI expression at the surface of human neutrophils in a FcgRII-dependent fashion: A crucial role for FcgRI in cellular responsiveness.

Autoimmune complexes are an important feature of several autoimmune diseases such as lupus, as they contribute to tissue damage through the activation of immune cells. Neutrophils, key players in lupus, interact with immune complexes through Fc gamma receptors (FcgR). Incubation of neutrophils with aggregated-IgGs caused degranulation and increased the surface expression of FcgRI within minutes in a concentration-dependent fashion. After 30 min, IgG aggregates (1 mg/ml) up-regulated FcgRI by 4.95 {+/-} 0.45-fold. FcgRI-positive neutrophils reached 67.24% {+/-} 6.88% on HA-IgGs stimulated neutrophils, from 3.12% {+/-} 1.62% in non-stimulated cells, ranking IgG-aggregates among the most potent known agonists. FcgRIIa, and possibly FcgRIIIa, appeared to mediate this up-regulation. Also, FcgRI-dependent signaling proved necessary for reactive oxygen species (ROS) production in response to IgG-aggregates. Finally, combinations of bacterial materials with aggregates dramatically boosted ROS production. This work suggests FcgRI as an essential component in the response of human neutrophils to immune complexes leading to the production of ROS, which may help explain how neutrophils contribute to tissue damage associated with immune complex-associated diseases, such as lupus.

immunology↗