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Cellular Components of Blood
Published in Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal, Principles of Physiology for the Anaesthetist, 2020
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal
Phagocytosis refers to the cellular ingestion of foreign material (bacteria, fungi) or dead or damaged cells of the host. The foreign particle is opsonized with immunoglobulin or complement, and this enables the neutrophils and monocytes to recognize the foreign material as they possess Fc and C3b receptors. The binding of phagocytes to particles coated with IgG or C3 results in activation of phagocytosis (Figure 51.11).
Host-Parasite Interactions With Macrophages In Culture
Published in Hans H. Gadebusch, Phagocytes and Cellular Immunity, 2020
Lee S. F. Soderberg, Morris Solotorovsky
Analysis of the molecular events involved in phagocytosis is advancing our understanding of this most basic function. Chemotactic factors may selectively attract certain phagocyte populations to a particular site, perhaps for a particular function. Macrophages then recognize and bind foreign materials. Recognition is not specific in differentiating antigens, but these cells recognize self from nonself at least in some cases by Fc and complement receptors and also possibly by surface membrane charges. Distinct particles may attach to different areas of the macrophage membrane and electron microscopy suggests that the process of ingestion may vary depending on the site of binding and the particle attached. Intracellular killing is probably mediated through some intermediate of peroxide metabolism although certain microorganisms may be killed by alternative mechanisms.
Inflammation and immunology
Published in C. Simon Herrington, Muir's Textbook of Pathology, 2020
Christopher Bellamy, Stephen J. Jenkins, Henry J. McSorley, David A. Dorward, Timothy J. Kendall
Phagocytosis involves the cellular events of recognition, attachment and engulfment of particles, which in the case of live microorganisms is followed by killing, then breakdown (Figures 4.5 and 4.6). The most important phagocytes in inflammation are the neutrophils and the macrophages. Neutrophils originate and mature in bone marrow before entering the circulation where they comprise 40%–60% of white blood cells. They are the first cell type to be recruited to acutely inflamed sites and since they cannot proliferate, can be replenished only by further recruitment from the circulation. Neutrophils are both highly secretory cells, which help in the first stages of breakdown of damaged and dead tissue, and are highly proficient at phagocytosis and killing of bacteria. Unlike neutrophils, which are not usually prevalent in normal tissue, most tissues have a normal tissue-resident population of macrophages. These and other sentinel cells are critical to the early recognition and response to danger signals. Macrophages can proliferate, but their numbers are also increased during inflammation by the exit from the circulation and maturation of bone marrow-derived monocytes. Macrophages are mature but multi-functional immune cells, with important roles in killing of some microbes, scavenging debris, phagocytosing dead cells and aiding in tissue repair or scarring.
Bispecific antibodies for immune cell retargeting against cancer
Published in Expert Opinion on Biological Therapy, 2022
Rebecca P Chen, Kenta Shinoda, Pragya Rampuria, Fang Jin, Tin Bartholomew, Chunxia Zhao, Fan Yang, Javier Chaparro-Riggers
Phagocytosis is a cellular process that macrophages and other phagocytes utilize to engulf and internalize large particles, including pathogens and dead cells. It can be mediated by complement receptors, FcγRs, and scavenger receptors, which include a large group of cell-surface receptors that bind non-self and altered-self ligands, resulting in subsequent destruction and elimination of the internalized cell material. Importantly, FcγRs on macrophages are ligated by antibody Fc fragments to initiate antibody-dependent cellular phagocytosis (ADCP), a mechanism linking innate and adaptive immunity. Multiple preclinical models have shown that ADCP is tumoricidal, as macrophages can phagocytose antibody-opsonized tumors [154]. Phagocytosis of apoptotic cells, termed efferocytosis, resolves inflammation and dampens immune response [155].
Primary Immunodeficiency and Thrombocytopenia
Published in International Reviews of Immunology, 2022
Maryam Mohtashami, Azadehsadat Razavi, Hassan Abolhassani, Asghar Aghamohammadi, Reza Yazdani
Phagocytes such as monocytes, macrophages, neutrophils, dendritic cells and eosinophils are principally responsible for the phagocytosis process. Phagocytosis may be defined as a major immunity mechanism eliminating pathogen agents and apoptotic cells by the engulfment process [127]. Neutrophils, as a main phagocytic cell, are one of the most abundant cells in innate immunity involved in the primary response to infection and inflammatory conditions [128]. Not only neutrophils can directly adhere to damaged endothelium, but also resident platelets recruit neutrophils by the interaction between P-selectin and counter-receptor, P-selectin glycoprotein (PSGL-1). This interaction ultimately stimulates neutrophil extracellular trap (NET) formation resulted in intrinsic activation and extrinsic pathway of coagulation [129, 130]. Studies have shown that platelet adhesion to neutrophils leads to provoke the NETosis and accelerate phagocytosis [131].
Recent advances in high-throughput flow cytometry for drug discovery
Published in Expert Opinion on Drug Discovery, 2021
Phagocytosis is one of the main mechanisms of immune defense by which abnormal particles, foreign microorganisms, apoptotic, infected, damaged or cancerous cells are ingested and destroyed. Several type of immune cells, including neutrophils, macrophages, dendritic cells, monocytes and B cells can perform phagocytosis [65]. Several groups have reported the development of bead-based HTFC phagocytosis assays [54,66–71]. These HTFC phagocytosis assays have been developed in: THP-1 cells, human and mouse neutrophils and human whole blood, to determine the phagocytic activity of clinical antibody samples; antibody-mediated phagocytosis against an array of viruses, including influenza, HIV, Ebola and dengue; and to investigate human immune response during tuberculosis infection. All these reported phagocytosis assays involve the use of antigen-coated fluorescent beads, which allow the formation of antigen-specific antibody/antigen immune complexes to be taken up by phagocytes upon binding of Fc receptors. Bead-based flow cytometry phagocytosis assays offer the sample sparing, antigenically flexible, high-throughput advantages over other phagocytosis assays, such as imaging assays using fluorescein or rhodamine-labeled particles, ethidium bromide uptake assay and assays using pH-sensitive fluorescence dyes.