Structure and function of skin
Roger L. McMullen in Antioxidants and the Skin, 2018
When tissues are invaded by foreign substances (pathogens), such as bacteria, viruses, fungi, or parasites, the infected cells are able to communicate their distress through cellular signaling. This leads to mobilization of phagocytic cells, which circulate in the blood stream, and migrate to areas of tissue injury where they seek pathogens and destroy them. Typically, phagocytes are white blood cells (leukocytes), which function by engulfing the pathogen and encasing it in a vacuole within its cytoplasm. Table 1.3 contains a list of phagocytes typically found in skin. Of the cell types listed, neutrophils, eosinophils, and basophils belong to the granulocyte class of leukocytes. This cell type reacts very quickly to pathogen invasion, unlike the mast cell, which is slower to mobilize. The mast cell, however, is longer lived than the granulocytes.
Dermal filler complications and management
Michael Parker, Charlie James in Fundamentals for Cosmetic Practice, 2022
Phagocytes are a family of cells comprised of macrophages and neutrophils which engulf and digest microbes and cellular debris. By digesting unwanted bacteria and debris, the surrounding environment can be cleansed to allow for the eradication of infection and proper wound healing. Infections cause the release of cytokines which attract phagocytes to the affected area. As they migrate, macrophages differentiate and change their behaviour, some become wandering macrophages that become larger and begin to hunt down pathogens and toxic debris, whereas other macrophages will become fixed macrophages and stand guard within specific tissues to anticipate any potential spread of infection. Alongside their direct role in removing harmful pathogens and material from an area of infection, macrophages also play a key role in mediating inflammation and wound healing, as discussed previously.
Potential of Herbal Extracts and Bioactive Compounds for Human Healthcare
Megh R. Goyal, Hafiz Ansar Rasul Suleria, Ramasamy Harikrishnan in The Role of Phytoconstitutents in Health Care, 2020
As long as the phagocytes work efficiently, there is no need to trigger acquired immunity. For example, in innate immunity, phagocytes (such as macrophages and neutrophils) produce different types of antimicrobial compounds that play an important role in the immune system. The main function of the phagocytes is to remove or eliminate the microorganisms or other dead bodies. Neutrophils possess phagocytosis, which have an important role in host defense against infectious agents. The innate immunity and the phagocytosis of macrophages provide the first barrier against infection and in acquired immunity, which contributes to regulate both humoral and cellular immune functions [438]. The phagocytosis has a burst through oxidative metabolism that results in the generation of ROS, which can be determined by NBT assay to confirm the intracellular killing activity of phagocytosis macrophage [697]. Phagocytosis is the primary defense mechanism against any foreign body entering the body, which is offered by neutrophils and macrophages.
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].
Phagocytosis: Phenotypically Simple Yet a Mechanistically Complex Process
Published in International Reviews of Immunology, 2020
The mTOR promotes vesicle fission from the phagosome in a vacuolar H+-adenosine triphosphatase ATPase (V-ATPase)-dependent manner, which occurs in parallel to the lysosome reformation from autophagolysosomes [342,343]. Thus, the macroendocytic vacuole formation during the late stage of phagocytosis or the entosis (the engulfment of live cells) involves the processing of large vacuoles by mTOR-dependent membrane fission mechanism. The inhibition of the mTOR signaling pathway increases the size of associated phagosomal vacuole that is closely apposed to the phagosome [344]. The identification of this vacuolar compartment will prove helpful to understand the subcellular trafficking involved in the destruction of phagocytosed anti-body opsonized cells or pathogens. The downstream mTOR signaling controlling the fission of phagolysosomes or autophagolysosomes is still not clear. However, an increased mTOR activity attenuates autophagy and generates proto-lysosomal tubules and vesicles, which extrude from autolysosomes These proto-lysosomal tubules and vesicles mature into functional lysosomes independent of IRAK1/4 (Interleukin-1 receptor-associated kinase 1 or 4) and TBK (TANK binding kinase) during TLR-mediated signaling in the presence of PI3K [345,346]. Hence, the phagocytic process is not merely to engulf the pathogens or dying cells but to digest them accordingly as per the need for the host to maintain the homeostasis.
Polymeric nanostructure vaccines: applications and challenges
Published in Expert Opinion on Drug Delivery, 2020
Rosana Simón-Vázquez, Mercedes Peleteiro, África González-Fernández
Since then, the use of polymeric micro and nanostructures as Ag and adjuvant carriers has raised a great interest because they have a similar size than the pathogens, and hence, the phagocytic cells like macrophages and dendritic cells (DCs) can easily recognize and uptake them [13]. Neutrophils, macrophages, and DCs are all professional phagocytes but show differences regarding the phagocytic process. While neutrophils and macrophages recognize and destroy the phagocytosed elements very fast, DCs process the ingested element differently, in order to initiate an adaptive immune response. It has been observed that both, phagosomal degradation and acidification, are lower in DCs than in the other phagocytes, helping to preserve the antigenic peptides and improving Ag presentation to naïve T cells [14].