The Antibody Receptor Fc Gamma Receptor IIIb Induces Calcium Entry via Transient Receptor Potential Melastatin 2 in Human Neutrophils

Current development of Fc gamma receptors (FcγRs) in diagnostics: a review

The ability of the immune system to fight against pathogens relies on the intricate collaboration between antibodies and Fc gamma receptors (FcγRs). These receptors are a group of transmembrane glycoprotein molecules, which can specifically detect and bind to the Fc portion of immunoglobulin G (IgG) molecules. They are distributed on a diverse array of immune cells, forming a strong defence system to eliminate invading threats. FcγRs have gained increasing attention as potential biomarkers for various diseases in recent years due to their ability to reflect immune dysregulation and disease pathogenesis. Increasing lines of evidence have shed new light on the remarkable association of FcγRs polymorphisms with the susceptibility of autoimmune diseases such as systemic lupus erythematosus (SLE) and lupus nephritis. Several studies have also reported the application of FcγR as a novel biomarker for the diagnosis of infection and cancer. Due to the surge in interest and concern regarding the potential of FcγRs as promising diagnostic biomarkers, this review, thereby, serves to provide a comprehensive overview of the structural characteristics, functional roles, and expression patterns of FcγRs, with a particular focus on their evolving role as diagnostic and prognostic biomarkers.

Antibody-mediated control mechanisms of viral infections

Antibodies generated after vaccination or natural pathogen exposure are essential mediators of protection against many infections. Most studies with viruses have focused on antibody neutralization, in which protection is conferred by the fragment antigen binding region (Fab) through targeting of different steps in the viral lifecycle including attachment, internalization, fusion, and egress. Beyond neutralization, the fragment crystallizable (Fc) region of antibodies can integrate innate and adaptive immune responses by engaging complement components and distinct Fc gamma receptors (FcγR) on different host immune cells. In this review, we discuss recent advances in our understanding of antibody neutralization and Fc effector functions, and the assays used to measure them. Additionally, we describe the contexts in which these mechanisms are associated with protection against viruses and highlight how Fc-FcγR interactions can improve the potency of antibody-based therapies.

Single-cell atlas of human gingiva unveils a NETs-related neutrophil subpopulation regulating periodontal immunity

INTRODUCTION

Exaggerated neutrophil recruitment and activation are the major features of pathological alterations in periodontitis, in which neutrophil extracellular traps (NETs) are considered to be responsible for inflammatory periodontal lesions. Despite the critical role of NETs in the development and progression of periodontitis, their specific functions and mechanisms remain unclear.

OBJECTIVES

To demonstrate the important functions and specific mechanisms of NETs involved in periodontal immunopathology.

METHODS

We performed single-cell RNA sequencing on gingival tissues from both healthy individuals and patients diagnosed with periodontitis. High-dimensional weighted gene co-expression network analysis and pseudotime analysis were then applied to characterize the heterogeneity of neutrophils. Animal models of periodontitis were treated with NETs inhibitors to investigate the effects of NETs in severe periodontitis. Additionally, we established a periodontitis prediction model based on NETs-related genes using six types of machine learning methods. Cell-cell communication analysis was used to identify ligand-receptor pairs among the major cell groups within the immune microenvironment.

RESULTS

We constructed a single-cell atlas of the periodontal microenvironment and obtained nine major cell populations. We further identified a NETs-related subgroup (NrNeu) in neutrophils. An in vivo inhibition experiment confirmed the involvement of NETs in gingival inflammatory infiltration and alveolar bone absorption in severe periodontitis. We further screened three key NETs-related genes (PTGS2, MME and SLC2A3) and verified that they have the potential to predict periodontitis. Moreover, our findings revealed that gingival fibroblasts had the most interactions with NrNeu and that they might facilitate the production of NETs through the MIF-CD74/CXCR4 axis in periodontitis.

CONCLUSION

This study highlights the pathogenic role of NETs in periodontal immunity and elucidates the specific regulatory relationship by which gingival fibroblasts activate NETs, which provides new insights into the clinical diagnosis and treatment of periodontitis.

Phagosomal granulocytic ROS in septic patients induce the bacterial SOS response

Septic patients with worst clinical prognosis have increased circulating immature granulocytes (IG), displaying limited phagocytosis and reactive oxygen species (ROS) production. Here, we developed an ex vivo model of incubation of human granulocytes, from septic patients or healthy donors, with Escherichia coli. We showed that the ROS production in Sepsis-IG is lower due to decreased activation and protein expression of the NADPH oxidase complex. We also demonstrated that the low level of ROS production and lower phagocytosis of IG in sepsis induce the bacterial SOS response, leading to the expression of the SOS-regulated quinolone resistance gene qnrB2. Without antimicrobial pressure, the sepsis immune response alone may promote antibiotic resistance expression.

ROS-Activated TRPM2 Channel: Calcium Homeostasis in Cardiovascular/renal System and Speculation in Cardiorenal Syndrome

The transient receptor potential melastatin 2 (TRPM2) channel is a nonselective calcium channel that is sensitive to oxidative stress (OS), and is widely expressed in multiple organs, such as the heart, kidney, and brain, which is inextricably related to calcium dyshomeostasis and downstream pathological events. Due to the increasing global burden of kidney or cardiovascular diseases (CVDs), safe and efficient drugs specific to novel targets are imperatively needed. Notably, investigation of the possibility to regard the TRPM2 channel as a new therapeutic target in ROS-related CVDs or renal diseases is urgently required because the roles of the TRPM2 channel in heart or kidney diseases have not received enough attention and thus have not been fully elaborated. Therefore, we aimed to review the involvement of the TRPM2 channel in cardiovascular disorders related to kidney or typical renal diseases and attempted to speculate about TRPM2-mediated mechanisms of cardiorenal syndrome (CRS) to provide representative perspectives for future research about novel and effective therapeutic strategies.

Human neutrophil Fc gamma receptors: different buttons for different responses

Neutrophils are fundamental cells in host defense. These leukocytes are quickly recruited from the blood to sites of infection or tissue damage. At these sites, neutrophils initiate several innate immune responses, including phagocytosis, production of reactive oxygen species, degranulation to release proteases and other antimicrobial compounds, production of inflammatory mediators, and formation of neutrophil extracellular traps. In addition to their role in innate immunity, neutrophils are now recognized as cells that also regulate adaptive immunity, via interaction with dendritic cells and lymphocytes. Neutrophils also respond to adaptive immunity by interacting with antibody molecules. Indeed, antibody molecules allow neutrophils to have antigen-specific responses. Neutrophils express different receptors for antibodies. The receptors for immunoglobulin G molecules are known as Fcγ receptors. Upon Fcγ receptor aggregation on the cell membrane, these receptors trigger distinct signal transduction cascades that activate particular cellular responses. In this review, we describe the major Fcγ receptors expressed on human neutrophils and discuss how each Fcγ receptor activates a choice of signaling pathways to stimulate particular neutrophil responses.

The transient receptor potential channels in rheumatoid arthritis: Need to pay more attention

Rheumatoid arthritis (RA) is characterized by the augment of vascular permeability, increased inflammatory cells infiltration, dysregulated immune cells activation, pannus formation and unbearable pain hyperalgesia. Ca²⁺ affect almost every aspect of cellular functions, involving cell migration, signal transduction, proliferation, and apoptosis. Transient receptor potential channels (TRPs) as a type of non-selective permeable cation channels, can regulate Ca²⁺ entry and intracellular Ca²⁺ signal in cells including immune cells and neurons. Researches have demonstrated that TRPs in the mechanisms of inflammatory diseases have achieved rapid progress, while the roles of TRPs in RA pathogenesis and pain hyperalgesia are still not well understood. To solve this problem, this review presents the evidence of TRPs on vascular endothelial cells in joint swelling, neutrophils activation and their trans-endothelial migration, as well as their bridging role in the reactive oxygen species/TRPs/Ca²⁺/peptidyl arginine deiminases networks in accelerating citrullinated proteins formation. It also points out the distinct functions of TRPs subfamilies expressed in the nervous systems of joints in cold hyperalgesia and neuro-inflammation mutually influenced inflammatory pain in RA. Thus, more attention could be paid on the impact of TRPs in RA and TRPs are useful in researches on the molecular mechanisms of anti-inflammation and analgesic therapeutic strategies.

CD16+ fibroblasts foster a trastuzumab-refractory microenvironment that is reversed by VAV2 inhibition

The leukocyte Fcγ receptor (FcγR)-mediated response is important for the efficacy of therapeutic antibodies; however, little is known about the role of FcγRs in other cell types. Here we identify a subset of fibroblasts in human breast cancer that express CD16 (FcγRIII). An abundance of these cells in HER2⁺ breast cancer patients is associated with poor prognosis and response to trastuzumab. Functionally, upon trastuzumab stimulation, CD16⁺ fibroblasts reduce drug delivery by enhancing extracellular matrix stiffness. Interaction between trastuzumab and CD16 activates the intracellular SYK-VAV2-RhoA-ROCK-MLC2-MRTF-A pathway, leading to elevated contractile force and matrix production. Targeting of a Rho family guanine nucleotide exchange factor, VAV2, which is indispensable for the function of CD16 in fibroblasts rather than leukocytes, reverses desmoplasia provoked by CD16⁺ fibroblasts. Collectively, our study reveals a role for the fibroblast FcγR in drug resistance, and suggests that VAV2 is an attractive target to augment the effects of antibody treatments.