The Lymphatic/Immune System and Its Disorders
Walter F. Stanaszek, Mary J. Stanaszek, Robert J. Holt, Steven Strauss in Understanding Medical Terms, 2020
An antibody is an immunoglobulin molecule with a specific ammo acid sequence to react with its specific antigen or closely related antigens. Antibodies are divided on the basis of their action when in contact with the antigen. Agglutinins, for example, cause agglutination or clumping of the cells with the appropriate surface antigen, and bacter-iolysises cause bacteria to lyse or rapture so they are killed and their components can be removed from the body. Opsonins are antibodies that attach to a particulate antigen such as a bacterial cell or virion (virus particle) and make them susceptible to phagocytosis, a reaction that is essential in fighting infection by the many organisms resistant to ingestion by monocytes and neutrophils.
Gastrointestinal Tract as a Major Route of Pharmaceutical Administration
Shayne C. Gad in Toxicology of the Gastrointestinal Tract, 2018
Phagocytosis is Greek for “to devour” and involves the plasma membrane invaginating a solid particle into an internal compartment known as a phagosome. In this type of endocytosis, the cell changes shape by sending out projections around the substance. These projections are called pseudopodia or “false feet.” The cell wall is attracted to the substance by a chemical (chemotaxis). The cell sends out projections in the membrane that contact the substance making a non-specific receptor ligand interaction. Subsequently, the membrane projections engulf the substance eventually re-fusing the cell walls forming an intracellular vesicle. Phagocytosis in an organism’s immune system is a major mechanism used to remove pathogens and unnecessary cellular debris. Upon ingestion of a pathogenic microorganism by a macrophage, it becomes trapped in a phagosome which then fuses with a lysosome to form a phagolysosome. Within the phagolysosome, enzymes and toxic peroxides digest the pathogen. Debris such as bacteria, dead tissue cells, and small mineral particles are all examples of objects that may be phagocytized. The resulting waste material is discharged from the phagocyte by exocytosis. This type of endocytosis is limited to certain specialized cells such as neutrophils, macrophages, and amoeba so phagocytosis is not involved in the absorption of drugs per se (Freeman and Grinstein, 2014; Bourne, 2017; Rosales and Uribe-Querol, 2017).
The Human Immune System May Protect against HIV
Omar Bagasra, Donald Gene Pace in A Guide to AIDS, 2017
The word phago has reference to the eating process; the word cyto has reference to the cells. The term phagocytic, therefore, signifies a process in which cells that are dangerous or not useful are eaten-up by monocytes. Phagocytic cells eat fungi, bacteria, and parasites. It is interesting to note that neutrophils are the fastest replicating cells found in our body and any time their number decrease or their function is impaired, and the human body becomes highly vulnerable to microbial infection. These cells constantly circulate in our blood and infiltrate the area of what is invaded by a microbe. Besides phagocytic cells, other cells that circulate in our blood, although at much lower levels, are called monocytes. They also migrate to the different organs in the body, and play the role of a hungry garbage collector that eats nonfunctional cells and those cells that have died.
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].
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.
Role of macrophage in nanomedicine-based disease treatment
Published in Drug Delivery, 2021
Siwei Song, Hui Xia, Mengfei Guo, Sufei Wang, Shujing Zhang, Pei Ma, Yang Jin
Cellular uptake of nanomedicines is generally through phagocytosis (particles larger than 0.5 μm) and pinocytosis (uptake of fluids and solutes) (Patel et al., 2019). Phagocytosis is restricted to specialized phagocytic cells such as macrophages, neutrophils, monocytes, and dendritic cells. The phagocytic process begins with particle recognition and binding with receptors on the surface of the host cell, leading to the engulfment of particles into the cell and subsequent formation of phagosomes. Through a series of physical processes, the particle is transferred to late phagosomes and ultimately lysosomes, forming a phagolysosome (Sahay et al., 2010) (see Figure 2(A)). The physicochemical properties of nanomedicines often determine the efficiency of phagocytosis and the targeting effect of macrophages to the particles; these include shape, size, surface charge, suitable ligands, and so on. Table 1 lists several factors that affect the absorption of nanomedicines by macrophages.
Related Knowledge Centers
- Innate Immune System
- Multicellular Organism
- Phagosome
- Immune System
- Phagocyte
- Cell Membrane
- Pathogen
- Cell
- Endocytosis
- History of Phagocytosis