Bacterial Opsonization
Bacterial Opsonization - Related Videos
03:47
Determination of ROS Production by Neutrophils upon Interaction with Opsonized Biofilm
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2025
In this video, we demonstrate an in vitro chemiluminescence assay to detect the generation of reactive oxygen species by neutrophils upon exposure to an opsonized bacterial biofilm.
06:34
An Opsono-Adherence Assay for Assessing the Opsonization of Encapsulated Bacteria by Anti-Capsule Antibodies
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2025
This video demonstrates an opsono-adherence assay for examining the interaction between opsonized bacteria and immune cells. Fluorescently labeled bacteria, treated with test serum containing anti-capsule antibodies, are incubated with macrophages. After staining the macrophages with fluorescence, the attached bacteria on the macrophage surface are observed under a microscope for visualization.
03:22
Modeling Complement-Mediated Phagocytosis Using Opsonized Red Blood Cells In Vitro
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2026
Source: Nagre, N., et al. Alveolar Macrophage Phagocytosis and Bacteria Clearance in Mice. J. Vis. Exp. (2019).This video demonstrates the assessment of complement receptor-mediated phagocytosis using sheep red blood cells opsonized with IgM and complement, followed by their uptake by mouse macrophages. The extent of phagocytosis is quantified by measuring a blue chromogenic product formed through hemoglobin-catalyzed oxidation of diaminofluorene.
10:38
High Yield Purification of Plasmodium falciparum Merozoites For Use in Opsonizing Antibody Assays
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Cited by 18 •
2014
Measuring antibody function is key to understanding immunity to Plasmodium falciparum malaria. This method describes the purification of viable merozoites, and measurement of opsonization-dependent phagocytosis by flow cytometry.
04:33
Real-Time Imaging of Macrophage Phagocytosis of IgG-Opsonized Red Blood Cells
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2025
This video demonstrates an assay to monitor independent macrophage-mediated red blood cell (RBC) phagocytosis events. Mouse immunoglobulin G (IgG)-opsonized human RBCs are incubated with mouse macrophages and observed under a confocal microscope. The RBCs are engulfed by macrophages via a phagocytic cup formation and targeted for lysosomal degradation.
FAQs
The two major opsonin classes contribute through different recognition routes. IgG bound to a bacterium presents its Fc region to Fc receptors on macrophages and neutrophils, while C3b provides a complement-derived surface signal recognized by complement receptors. These parallel receptor interactions strengthen bacterial attachment to phagocytes, increasing the likelihood that engulfment and intracellular killing will follow.
Antibody-mediated and complement-mediated marking provide separate signals that converge on phagocytic cells. IgG engages receptors for antibody Fc regions, whereas C3b engages complement receptors on macrophages and neutrophils. Using both types of recognition can reinforce attachment to the bacterial surface and connect immune marking with the cellular steps required for removal.
Defects in either antibody or complement activity can weaken the signals that guide phagocytes toward bacteria. Without effective IgG or C3b deposition, macrophages and neutrophils may receive less efficient recognition and attachment cues. This impairment is especially relevant to defense against extracellular bacteria, which depends on their prompt removal and intracellular killing.
Opsonin binding alone does not complete bacterial clearance. Fc-region receptors and complement receptors on macrophages and neutrophils connect the coated bacterium to cellular responses. Their engagement promotes firm attachment, followed by engulfment and intracellular killing. Consequently, the effectiveness of the process depends on both surface marking and the ability of phagocytes to respond to those marks.
A useful sequence begins with IgG and complement proteins binding to the bacterial surface, followed by recognition through Fc-region and complement receptors on macrophages or neutrophils. The response then proceeds through attachment, engulfment, and intracellular killing. Tracking these stages helps distinguish inadequate coating from impaired phagocyte recognition or downstream clearance.
The central components are bacterial surfaces, IgG antibodies, complement proteins such as C3b, and phagocytic cells including macrophages and neutrophils. Their interactions explain how immune coating becomes cellular uptake. Examining these components together provides a framework for studying whether a defect lies in opsonin binding, receptor recognition, engulfment, or intracellular killing.
Bacterial opsonization provides a mechanistic context for understanding immune deficiency because impaired antibody or complement activity can reduce bacterial recognition and removal. Studying these defects links molecular immune components with susceptibility to infection, particularly from extracellular bacteria. The process therefore helps researchers relate deficient immune functions to failures in phagocyte attachment, engulfment, or killing.
The process offers a way to examine whether immune responses improve bacterial marking and phagocytic clearance. In vaccine research, attention can focus on antibody-mediated recognition, while antimicrobial studies can consider strategies that strengthen removal of coated bacteria. It also supports investigation of bacterial evasion, in which pathogens interfere with immune marking or its conversion into effective phagocyte activity.