Inhibitory affinity modulation of FcγRIIA ligand binding by glycosphingolipids by inside-out signaling

Comparison of oriented and non-oriented antibody conjugation with AIE fluorescence microsphere for the immunochromatographic detection of enrofloxacin

Antibodies and labels were typically non-oriented conjugated in conventional immunochromatographic assays (ICAs). In this work, a C-terminal cysteine-tagged recombinant protein A (rPA) was conjugated in an oriented manner onto aggregation-induced emission fluorescence microsphere (AIEFM). The Fc fragment of anti-enrofloxacin monoclonal antibody (anti-ENR mAb) was then conjugated onto the rPA. The resulting oriented mAb-AIEFM probe was used in an ENR-ICA for the rapid detection of ENR, a widely abused animal drug. The ENR-ICA with the oriented probe saved 66.7% of anti-ENR mAb and 25% of ENR-bovine serum albumin, and had a limit of detection of 0.035 ng/mL, compared with 0.079 ng/mL for the non-oriented probe. The corresponding linear ranges of the ENR-ICA based on the oriented and non-oriented probes were 0.25-10 ng/mL and 0.1-2.5 ng/mL, respectively. This novel ICA based on the oriented probe has the potential to be used for sensitive and rapid detection in food safety.

Multiplicity of Glycosphingolipid-Enriched Microdomain-Driven Immune Signaling

Glycosphingolipids (GSLs), together with cholesterol, sphingomyelin (SM), and glycosylphosphatidylinositol (GPI)-anchored and membrane-associated signal transduction molecules, form GSL-enriched microdomains. These specialized microdomains interact in a cis manner with various immune receptors, affecting immune receptor-mediated signaling. This, in turn, results in the regulation of a broad range of immunological functions, including phagocytosis, cytokine production, antigen presentation and apoptosis. In addition, GSLs alone can regulate immunological functions by acting as ligands for immune receptors, and exogenous GSLs can alter the organization of microdomains and microdomain-associated signaling. Many pathogens, including viruses, bacteria and fungi, enter host cells by binding to GSL-enriched microdomains. Intracellular pathogens survive inside phagocytes by manipulating intracellular microdomain-driven signaling and/or sphingolipid metabolism pathways. This review describes the mechanisms by which GSL-enriched microdomains regulate immune signaling.

The FcγRIII Engagement Augments PMA-Stimulated Neutrophil Extracellular Traps (NETs) Formation by Granulocytes Partially via Cross-Talk between Syk-ERK-NF-κB and PKC-ROS Signaling Pathways

Polymorphonuclear neutrophils (PMNs) are the most abundant white blood cell in the circulation capable of neutrophil extracellular traps (NETs) formation after stimulation. Both NADPH oxidase-dependent and -independent pathways are involved in NET formation. The IgG is the most abundant immunoglobulin in human serum. However, the impact of the circulating IgG on NET formation is totally unexplored. In this study, the all-trans retinoic acid (ATRA)-induced mature granulocytes (dHL-60) were pre-treated with monomeric human IgG, papain-digested Fab fragment, crystallizable IgG Fc portion, rituximab (a human IgG1), or IgG2. The NET formation of the dHL-60 in the presence/absence of phorbol 12-myristate 13-acetate (PMA) stimulation was then measured by the fluorescent area after SYTOX green nucleic acid stain. The intracellular reactive oxygen species (ROS) generation was measured by flow cytometry. Total and phosphorylated Syk, SHP-1, and ERK were detected by immunoblot. We found that human monomeric IgG and its subclasses IgG1 and IgG2 per se induced negligible NET formation of dHL-60, but the FcγRIII engagement by these IgG subclasses and Fc portion augment PMA-stimulated dHL-60 NET formation in a dose-dependent manner. Furthermore, we found that increased Syk and ERK phosphorylation, intracellular ROS generation, and pro-inflammatory cytokines, IL-8 and TNF-α, production could be induced after FcγRIII engagement. Blocking FcγRIII engagement by a specific antibody diminished the augmented NET formation. In conclusion, we discovered that cross-talk between FcγRIII engagement-induced Syk-ERK and PMA-induced PKC signaling pathways augment NET formation of dHL-60 via increased ROS generation and pro-inflammatory cytokines, IL-8 and TNF-α, production.