Biological Sciences
Phagocytosis
Phagocytosis is a process by which cells engulf and digest foreign particles, such as bacteria and debris, to remove them from the body. It is a vital component of the immune system's response to infection and plays a key role in maintaining tissue homeostasis. Phagocytosis is primarily carried out by specialized cells, including macrophages and neutrophils, and is essential for protecting the body against pathogens.
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8 Key excerpts on "Phagocytosis"
eBook - PDF- A.G. Lee(Author)
- 1996(Publication Date)
- Elsevier Science(Publisher)
Phagocytosis Eric J. Brown and Thomas H. Steinberg I. Introduction 34 II. Phagocytic Receptors 36 A. IgG Fc Receptors 37 B. Complement Receptors 40 C. Mannose Receptors 42 D. Cooperation between Phagocytic Receptors 42 III. Models and Potential Models for Phagocytosis 43 A. Transfection of Phagocytic Receptors 43 B. Unicellular Organisms 44 IV. Phagocytosis and Signal Transduction 44 A. Protein Kinases 45 B. Cytosolic Calcium 46 C. Phospholipases 47 D. Cytokines 47 V. Phagocytosis and Cytoskeleton 47 A. Cytoskeleton and Signal Transduction 49 B. Paxillin 49 C. MARCKS 49 D. GTP Binding Proteins 50 E. Myosins 50 Biomembranes Volume 4, pages 33-63. Copyright © 1996 by JAI Press Inc. All rights of reproduction in any form reserved. ISBN: 1-55938-661-4. 33 34 ERIC J. BROWN and THOMAS H. STEINBERG VI. Regulation of Phagocytosis 51 A. Cytokine Activation of Phagocytosis 51 B. Extracellular Matrix Activation of Phagocytosis 52 C. Two Pathways for Activation of PMN Phagocytosis 53 VII. Intracellular Events Following Phagocytosis 54 A. Fusion Events Following Phagocytosis 54 B. Intracellular Infection 55 VIII. Beyond the Zipper Hypothesis 55 IX. Conclusions 57 Acknowledgments 57 References 57 I. INTRODUCTION Phagocytosis is the process by which cells ingest other cells and cell fragments, bacteria, and particles >1 jum in diameter. This activity takes a variety of forms and achieves a number of goals. For example, free-living amoeba ingest bacteria and other organisms for nourishment and the roots of leguminous plants harbor nitro-gen-fixing bacteria within compartments resembling phagocytic vacuoles and benefit from this nitrogen-fixing capacity. In mammalian cells, the most prominent roles for Phagocytosis are degradative, either to remove tissue debris and dead cells (maintenance) or to destroy invading pathogens (host defense).
eBook - PDF- Edwin L. Cooper(Author)
- 2014(Publication Date)
- Pergamon(Publisher)
CHAPTER 10 Phagocytosis Introduction Phagocytosis by Macrophages Introduction Mechanisms of uptake of extracellular material Hffects of humoral factors The Process in Neutrophils Killing by Phagocytic Cells 119 The myeloperoxidase system 124 119 Alterations in metabolism 124 119 Phagocytosis in Hibernating Mammals 125 120 Temperature and Phagocytosis in Teleost Fishes 126 122 Involution of the Mononuclear Phagocytic System 127 122 Phagocytosis in Invertebrates 127 124 Final Comment 129 INTRODUCTION Since infectious microorganisms can enter the body at many points, cellular sentinels must stand guard throughout it. Connective tissue contains phagocytic cells (e.g. macrophages) and blood contains monocytes and granulocytes which show varying degrees of Phagocytosis. We know a great deal about neutrophils and their prime role in Phagocytosis; however, eosinophils and basophils are not primarily phagocytes. Phagocytosis is one important function of certain cells of the immune system, and for this reason the process merits this chapter's description. Neutrophils, which play an important role as scavenger cells, are joined by several other cell types capable of Phagocytosis: alveolar phagocytes of the lung, microglia of the brain, reticular cells of bone marrow, spleen and lymph nodes,, and the Von Kupffer cells of the liver. Because all of these cells phagocytose, they are often grouped together and referred to as the macrophage system. Since in the liver, spleen and bone marrow they are strategically located to act as special endothelia or cells that line sinusoids through which blood flows, they have also been referred to as the reticuloendothelial system (RES), a term which is frequently criticized, since more terms create more confusion. Other cells unrelated to macrophages may show evidence of Phagocytosis: epithelia, fat cells, fibrocytes, etc.
eBook - PDF- Anthony A. Nash, Cedric A. Mims, John Stephen(Authors)
- 2000(Publication Date)
- Academic Press(Publisher)
The specialised phagocytic cells are therefore equipped with a powerful array of antimicrobial weapons and lysosomal enzymes. Cell Biology of Phagocytosis Pinocytosis (the uptake of fluid and solutes) and receptor-mediated endocytosis share a clathrin-based mechanism which usually is 86 Mims Pathogenesis of Infectious Disease independent of actin polymerisation. In contrast, Phagocytosis is involved in the uptake of larger particles, is usually clathrin-indepen- dent and occurs by an actin-dependent mechanism. Phagocytosis is a highly complex phenomenon the molecular details of which are now beginning to be unravelled. A brief summary of some of the main features of this rapidly developing area is given as it will help our understanding of the material here and in Chapter 8. Receptors/ligands Before Phagocytosis can take place there must be preliminary (non- specific) attachment of the object to the phagocytic cell surface, followed by firmer specific attachment. The firm attachment and certainly the ingestion of particles is facilitated by serum substances called opsonins which then act as ligands. Opsonins include acquired or naturally occurring antibodies, and complement. Opsonin comes from a Greek word meaning sauce or seasoning; it makes the microbe more palatable and more easily ingested by the phagocyte. Initiation of internalisation involves interaction between opsonins on the particle and surface receptors on the phagocyte. Receptor/ligand complexes comprise the initial link in the complex train of signal transduction events in the cell which in the case of the phagocyte ultimately involves the cytoskeleton. Two of the best characterised receptors in macrophages are the complement receptor 3 (CR3) which binds C3bi on complement-opsonised targets and Fc gamma receptors (FcyRs) which bind to antibody-coated targets (see below).
eBook - PDF- G. E. W. Wolstenholme, Maeve O'Connor, G. E. W. Wolstenholme, Maeve O'Connor(Authors)
- 2009(Publication Date)
- Wiley(Publisher)
This immunological cell Phagocytosis has been thoroughly investigated, both experimentally in animals and pathologic- ally in man. Morphological data relating to it are fairly ex- tensive and concern tlie uptake of red blood cells, platelets, whole leucocytes and leucocyte nuclei. This has already been studied in an earlier publication (Robineaux, 1054) which may be referred to for details. Generally speaking, cell phagocyto- sis which in uitro is achieved both by polynuclear cells and histiocytes, seems to be, in uiuo, a function essentially reserved for histiocytes. Here again, tlie predominant notion is that the cells, or cell elements, liavirig been enveloped by Eiyaloplasmic veils through a mechanism very similar to that described earlier for bacteria, adhere to the pliagocytc. Immuiic cell Phagocytosis is obviously closely associated with the preence, in the medium, of opsonins and comple- ment, in the same way as bacterial Phagocytosis. Here again, it can be said that Phagocytosis is promoted in two ways by the complement, which is fixed on the antigen-antibody com- plex : by forming highly adherent complexes, and by even- tually stimulating the mobility functions. The antigenic complexity of the ingested structures, whether heterologous, irologous, or even autologous, which have become antigenic through acquired incompatibility, can be imagined. In the latter case, physiological Phagocytosis of blood elements is transformed into immune Phagocytosis, pro- ducing an accelerated Phagocytosis of sensitized elements. Many instances of immune Phagocytosis through auto- sensitization, involving red blood cells and leucocytes as well SOME MECHANISMS OF ANTIGEN UPTAKE BY CELLS 21 as platelets, can be found in human pathology. These last few years, our efforts have becn directed to one aspect of auto- sensitization.
eBook - PDF- S. Gordon(Author)
- 1999(Publication Date)
- Elsevier Science(Publisher)
SECTION I CONTEXT This Page Intentionally Left Blank TH E EARLY H ISTORY OF Phagocytosis Thomas R Stossel I. Introduction ....................................................... 3 II. The Initial Descriptions of Phagocytosis .................................. 5 III. Early Studies of the Mechanism of Phagocytosis ......................... 10 IV. Discovery of Leukocytes and Their Trafficking ........................... 11 V. The MetchnikoffSynthesis 14 Acknowledgments ................................................. 16 References ....................................................... 16 I. INTRODUCTION This book summarizes the state of knowledge of the science ofPhagocytosis as we enter the third millenium. Like the rest of biological science at this moment, Phagocytosis is approaching a level of fundamental comprehension previously limited to the physical sciences, and the practical spinoffs of this knowledge have bright commercial and medical possibilities. Yet Phagocytosis was a subject of interest to biologists long before the emergence of modern cell and molecular biol- Advances in Cell and Molecular Biology of Membranes and Organelles Volume 5, pages 3-18. Copyright 9 1999 by JAI Press Inc. All rights of reproduction In any form reserved. ISBN: 1-55938-999-0 4 THOMAS P. STOSSEL ogy, indeed, two centuries before the molecular definition of a genetic code. So what? Historians argue that a decent and rich life requires an understanding of ones precedents, and that a perception of how small any individual is in the vast tapes- try of history affords the humility that engenders character. However, many dis- miss history as an irrelevant graveyard at best and an instrument of political oppression at worst: the tyranny ofdead white males. Scientists tend to have such an attitude by default.
eBook - PDF- Edward Bittar(Author)
- 1996(Publication Date)
- Elsevier Science(Publisher)
Phagocytes in Immunity and Inflammation 201 is not random but instead involves a highly regulated communication network and specific targeting events. Extracellular signaling molecules known as chemoattrac-tants are generated at the target site by the microbe, as well as by the host in response to the microbe. As the chemoattractant diffuses out from the target site, phagocytes detect it by means of specific cell surface receptors. The spatial and temporal interaction of the receptors with the chemoattractant conveys information to the cell regarding the location of the target. In response to this information, the cell extensively remodels its cytoskeleton, and biases its otherwise random movements in the direction of higher concentrations of the chemoattractant, thereby moving towards the target. This is known as chemotaxis. Phagocytes leave the bloodstream by crawling between vascular endothelial cells, in a complex process known as diapedesis. The phagocyte recognizes and binds to the target most efficiently when it has first been decorated with molecular tags such as specific antibodies or generic complement fragments, for which it possesses additional sets of receptors. The tagging process is known as opsonization (from the Greek for to prepare food). The phagocyte then engulfs the bound target forming a cytoplasmic phagosome. Phagocytosis in turn triggers the delivery of antimicrobial proteins and digestive enzymes to the phagosome by fusion with cytoplasmic granules, and the production of an array of germ-killing oxidants by activation of a latent NADPH oxidase. Phagocytes and Immunity Immunity can be operationally defined as the phenomenon whereby sublethal natural infection with a pathogenic microorganism, or exposure to its products, induces changes in the host that protect it from disease upon subsequent challenge with the same or a related organism. Vaccination is the intentional exploitation by man of this natural phenomenon.
eBook - PDF- Brian Ceresa(Author)
- 2012(Publication Date)
- IntechOpen(Publisher)
Namely, Mycobacterium tuberculosis (MTB) cells are easily trapped in the phagosomes of alveolar macrophages. However, these cells are not digested by macrophages, because the fusion of the MTB-containing phagosomes with lysosomes, which are indispensable for the digestion of bacteria inside phagosomes, is inhibited. As a result, MTB cells proliferate and accumulate inside macrophages [3]. Hence, the delivery of particles containing antituberculosis agents to alveolar macrophages would be expected to be effective for TB therapy. As summarized in Figure 1, endocytic uptake including Phagocytosis is classified according to the mechanism of vesicle formation as well as the size of particles ingested [4-7]. Phagocytosis is performed by specialized cells such as macrophages, and it plays a role in the clearance of particles having a diameter greater than 0.5 m. On the other hand, © 2012 Hirota and Terada, licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Molecular Regulation of Endocytosis 414 pinocytosis occurs in all cells, including macrophages and cancer cells, for obtaining nutrients and biological mediators. It is noteworthy that macropinocytosis covers a broad range of particle sizes from 100 nm to 5 m [8-10]. Figure 1. Classification of endocytosis in relation to particle sizes favorable for ingestion. In this chapter, features of Phagocytosis of particles in terms of particle properties, as well as Phagocytosis-induced physiological events of macrophages, are described. In addition, the promising aspect of clinical treatment by the utilization of endocytosis-mediated drug action is reviewed. 2. Effect of particle properties on endocytosis Drug-containing particle formulations are commonly used for delivery of drugs.
eBook - PDF- Eric Denkers, Ricardo T. Gazzinelli(Authors)
- 2007(Publication Date)
- CRC Press(Publisher)
Although macrophage function depends, at least in part, on location, developmental state and in vitro culture conditions, there are some properties that are conserved amongst almost all macrophage populations studied to date. One of the most distinctive properties of macroph ages is their ability to ingest particles via Phagocytosis. Macrophages are able to recognise both pathogens and noninfectious agents using a variety of germ line-encoded pattern recognition receptors including lectins, toll-like receptors, and receptors for N-formyl methionine contain ing peptides. Macrophages are involved in safe apoptotic cell clearance and remove small num bers of potentially dangerous micro-organisms via Phagocytosis without inducing a strong pro-inflammatory response. Should they fail to clear perceived threats, an acute inflammatory response is mounted. This results in the secretion of a variety of cytokines, chemokines and antimicrobial agents. Secretion of these mediators can result in autocrine activation of the macrophage by binding of cytokines to cytokine receptors or recruitment of cells involved in the adaptive immune response via secretion of chemokines. The macrophage destroys invading micro-organisms using an arsenal of antimicrobial effector mechanisms that encompass enzy matic degradation, oxidation, nutrient limitation and antimicrobial peptides. Upon internalisation and digestion of the pathogen, the macrophage presents foreign antigens to primed T lymphocytes, thus amplifying the adaptive immune response. When macrophage-based clearance is insufficient, prolonged or chronic inflammation may occur. Macrophages ♦Corresponding Author: S. Gordon— Sir William Dunn School of Pathology University of Oxford,10 South Parks Road, Oxford, 0X1 3RE. Email: [email protected] Protozoans in Macrophages , edited by Eric Denkers and Ricardo Gazzinelli. ©2007 Landes Bioscience.
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