Innate Immune System in Cardiovascular Diseases
Shyam S. Bansal in Immune Cells, Inflammation, and Cardiovascular Diseases, 2022
Specialized macrophages exist in all tissues (liver: Kupfer cells; lung: alveolar macrophages; brain: microglia; bone: osteoclasts; lymph nodes: histiocytes) and play essential roles in embryonic development, homeostasis, disease, and wound healing [20, 21]. Tissue-resident macrophages perform housekeeping and sentinel activities [22–24]. Macrophages engulf pathogens, foreign bodies, and cell debris through phagocytosis to function as antigen-presenting cells to the adaptive immune system, but they are equally important as moderators of the innate immune system through expression of cytokines and chemokines. Paradigm shifting studies have demonstrated that specialized tissue macrophages have a developmental origin that is distinct from that of monocytes and monocyte-derived macrophages that accumulate in infected and injured tissues. In mice, these cells are identified on the basis of lineage tracing and defined cell surface markers [13, 25–29].
Comparative Anatomy, Physiology, and Biochemistry of Mammalian Skin
David W. Hobson in Dermal and Ocular Toxicology, 2020
Another type of cell found in connective tissue is the macrophage. It is known by a variety of names such as clasmatocyte and histiocyte. The macrophage has been postulated to be derived from the monocyte. The life span may be 2 to 3 months, depending on the tissue. Macrophages can be identified by vital staining, an excellent method demonstrating macrophages “in action”. Ultrastructurally, macrophages have an irregular shape. Their cell membrane has been modified into finger-like projections or pseudopods. The nucleus is indented and common organelles such as mitochondria and a small amount of rough endoplasmic reticulum are present. Macrophages contain numerous types of lysosomes with pinocytotic and phagocytotic vacuoles. The function of macrophages is to engulf and destroy bacteria or foreign substances, and to process antigens for presentation to the immune system. The functional activity of a macrophage can be appreciated by the complexity of its membrane modifications.38,202,204
Host-Parasite Interactions With Macrophages In Culture
Hans H. Gadebusch in Phagocytes and Cellular Immunity, 2020
Differentiated from mesodermal tissue in embryogenesis, macrophages are found as disparate populations in many tissues. Concentrations of these cells appear in bone marrow, blood, serous cavities, liver, spleen, lungs, and connective tissue. Macrophages are characterized as large mononuclear phagocytes with an abundant cytoplasm and a spherical to indented nucleus. They attach avidly to glass and plastic surfaces, extending cytoplasmic processes and often displaying a ruffled membrane at a portion of the periphery of the cell. The cells are rich in catabolic enzymes, especially acid phosphatase and lysozyme. Macrophages differentiate from precursors formed in bone marrow. A brief (3-day half-time) enlistment as circulating monocytes precedes migration to the tissues as mature macrophages. The life history of this cell should include one additional step that may occur in vivo on contact with any of a variety of agents: activation. Inducing agents, such as thioglycollate, casein, and oil, or factors associ-ated with bacteria such as Listeria and mycobacteria can activate macrophages in vivo to a heightened metabolic level displaying enhanced phagocytic and bactericidal activ-ities. Activation due to microorganisms appears to be dependent upon T lymphocytes.’ Thymectomized or irradiated mice infected with Mycobacterium tuberculosis did not generate a population of activated macrophages as judged by the inability to overcome a nonspecific challenge with Listeria monocytogenes. Phagocytized substances and structures are digested by the catabolic enzymes contained within lysosomes.
Influencing tumor-associated macrophages in malignant melanoma with monoclonal antibodies
Published in OncoImmunology, 2022
Rebecca Adams, Gabriel Osborn, Bipashna Mukhia, Roman Laddach, Zena Willsmore, Alicia Chenoweth, Jenny L C Geh, Alastair D MacKenzie Ross, Ciaran Healy, Linda Barber, Sophia Tsoka, Victoria Sanz-Moreno, Katie E Lacy, Sophia N Karagiannis
Macrophages represent a diverse group of cells with multiple functions in health and disease.13 Historically, macrophages have been categorized into two broad subsets: M1 and M2.14 M1, or “classically activated” macrophages, are pro-inflammatory cells, polarized by lipopolysaccharide (LPS) and IFN-γ with important roles in mounting an innate response against microbial pathogens. Classical macrophages can phagocytose pathogens and foreign material and secrete inflammatory cytokines, such as IL-1β, IL-12, and TNF-α, IL-15, IL-6.13,15 Macrophages can also augment an adaptive immune response by presenting pathogenic antigens to the adaptive immune system.16 M2 “alternatively activated” macrophages exhibit a range of homeostatic and anti-inflammatory functions, involved in the resolution of inflammatory responses, promoting tissue repair and wound healing. They are polarized by Th2 cytokines, including IL-4 and IL-13, and express scavenger receptors, enabling the endocytosis of cellular and microbial debris.14,17,18 They secrete pro-angiogenic factors, such as VEGF and metalloproteinases, allowing remodeling of the extracellular matrix following an inflammatory reaction to restore homeostasis.19,20
Biodegradable and removable implants for controlled drug delivery and release application
Published in Expert Opinion on Drug Delivery, 2022
Vivek P Chavda, Gargi Jogi, Ana Cláudia Paiva-Santos, Ajeet Kaushik
One of the main drawbacks of implants, along with host immune rejection, is the surgical procedures. Once the implants are placed in the body, the defense systems recognize it as a foreign body, and this results in the initiation of immune reactions such as inflammation, hypersensitivity reactions, and rejection of implants. This renders the activation of innate immunity, which helps in the protection of body against foreign materials [19]. Activation of innate immunity leads to production of helper T-cells and interleukins in the inflammatory phase (Vroman effect) that ultimately leads to fibrotic encapsulation [20]. As macrophages are phagocytic, macrophages will attempt to remove debris and destroy any foreign substance. In the recent years, researchers have used surface modification and different stimuli-responsive diffusive systems to overcome the rejection issues [20]. Advancement in technology led to administration of noninvasive implants using injectable solid implants. According to a study, fluorouracil-based pellets were formulated and extruded to a sufficient injectable diameter for the delivery of the anti-neoplastic agent. It showed good in-vivo release and robust in vitro in vivo correlation. Almost 100% drug release was observed after a period of 14 days [21]. Thus, fluorouracil-based implants were found to be suitable as an adjunct therapy for the treatment of cancer and patients undergoing tumor excision.
The Effect of CD226 on the Balance between Inflammatory Monocytes and Small Peritoneal Macrophages in Mouse Ulcerative Colitis
Published in Immunological Investigations, 2022
Juan Li, Feng Zhao, Qi Qin, Liu Yang, Yuan Jiang, Yongli Hou, Yazhen Wang, Wenjing Zhou, Liang Fang, Lihua Chen
Macrophages can be divided into tissue-resident macrophages and monocyte-derived macrophages (Davies et al. 2013). Monocytes are important macrophage origins. We tested if deletion of CD226 can alter the balance between monocytes and macrophages in the mouse model of UC. We found knockout of CD226 significantly elevated the percentage of iMos in UC mice (Figure 3A). In addition, CD226 showed diverse biological effects on different peritoneal macrophage subsets in UC. It was shown that knockout of CD226 reduced the percentage of SPMs, but had no effect on LPMs in UC mice (Figure 3B). Furthermore, we found that knockout of CD226 significantly reduced IL-6 and CCL-2 mRNA expression, but enhanced IL-10 mRNA expression in peritoneal macrophages of UC mice (Figure 3C). These data suggested the relieved colitis in CD226 KO mice is mainly due to the altered distribution and function of monocytes/macrophages.
Related Knowledge Centers
- Alveolar Macrophage
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- Kupffer Cell
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- Pathogen
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