Phagocyte: From 3 Different Sources
A cell in the immune system that can surround, engulf, and digest microorganisms, foreign particles, and cellular debris.
Phagocytes are found in the blood, spleen, lymph nodes, and alveoli (small air sacs) within the lungs.
Cells – including monocytes (a variety of LEUCOCYTES) in the blood and macrophages (see MACROPHAGE) in the tissues – that envelop and digest BACTERIA cells, cell debris and other small particles. Phagocytes are an essential part of the body’s defence mechanisms.
n. a cell that is able to engulf and digest bacteria, protozoa, cells and cell debris, and other small particles. Phagocytes include many white blood cells (see leucocyte) and *macrophages, which play a major role in the body’s defence mechanism. —phagocytic adj.
A large PHAGOCYTE that forms part of the RETICULO-ENDOTHELIAL SYSTEM. It is found in many organs and tissues, including connective tissue, bone marrow, lymph nodes, spleen, liver and central nervous system. Free macrophages move between cells and, using their scavenger properties, collect at infection sites to remove foreign bodies, including bacteria. Fixed macrophages are found in connective tissue.... macrophage
A process by which BACTERIA and other foreign particles in the body are ingested by monocytes in the blood and macrophages in the tissues (see under PHAGOCYTE) that envelop and digest bacteria, cells, cell debris and other small particles. Phagocytes are an essential part of the body’s defence mechanisms.... phagocytosis
A traditional absorbable SUTURE used in surgery for tying cut arteries and stitching wounds. Consisting of twisted COLLAGEN (from sheep or cattle intestines), catgut is absorbed by phagocytes (see under PHAGOCYTE) over a variable period. There are two types: plain, and chromatised or chromic. Synthetic absorbable sutures cause less reaction, have a predictable absorption period and are more e?ective.... catgut
This is part of the body’s defence mechanism that comprises a series of 20 serum peptides (see PEPTIDE). These are sequentially activated to produce three signi?cant effects: ?rstly, the release of small peptides which provoke in?ammation and attract phagocytes (see PHAGOCYTE); secondly, the deposition of a substance (component C3b) on the membranes of invading bacteria or viruses, attracting phagocytes to destroy the microbes; thirdly, the activation of substances that damage cell membranes – called lytic components – which hasten the destruction of ‘foreign’ cells. (See IMMUNOLOGY.)... complement system
Pre?x denoting large-sized cell – for example, a MACROPHAGE is a large PHAGOCYTE.... macr-/macro
One of the main types of white blood cell. Monocytes are phagocytes, and play an important role in the immune system.... monocyte
n. 1. a membrane, sheath, or other structure that encloses a tissue or organ. For example, the kidney, adrenal gland, and lens of the eye are enclosed within capsules. A joint capsule is the fibrous tissue, including the synovial membrane, that surrounds a freely movable joint. 2. a soluble case, usually made of gelatin, in which certain drugs are administered. 3. the slimy substance that forms a protective layer around certain bacteria, hindering their ingestion by phagocytes. It is usually made of *polysaccharide.... capsule
n. the process whereby damaged or degenerating nerve cells finally disintegrate and are removed by scavenger cells (*phagocytes).... neuronophagia
n. a serum *complement component that attaches itself to invading bacteria and apparently makes them more attractive to *phagocytes and thus more likely to be engulfed and destroyed.... opsonin
A collection of cells and proteins that works to protect the body from harmful microorganisms, such as bacteria, viruses, and fungi. It also plays a role in the control of cancer and is responsible for the phenomena of allergy, hypersensitivity, and rejection after transplant surgery.
The term innate immunity is given to the protection that we are born with, such as the skin and the mucous membranes that line the mouth, nose, throat, intestines, and vagina. It also includes antibodies, or immunoglobulins (protective proteins), that have been passed to the child from the mother. If microorganisms penetrate these defences, they encounter “cell-devouring” white blood cells called phagocytes, and other types of white cells, such as natural cellkilling (cytotoxic) cells. Microorganisms may also meet naturally produced substances (such as interferon) or a group of blood proteins called the complement system, which act to destroy the invading microorganisms.The 2nd part of the immune system, adaptive immunity, comes into play when the body encounters organisms that overcome the innate defences. The adaptive immune system responds specifically to each type of invading organism, and retains a memory of the invader so that defences can be rallied instantly in the future.
The adaptive immune system first must recognize part of an invading organism or tumour cell as an antigen (a protein that is foreign to the body). One of 2 types of response – humoral or cellular – is then mounted against the antigen.
Humoral immunity is important in the defence against bacteria. After a complex recognition process, certain B-lymphocytes multiply and produce vast numbers of antibodies that bind to antigens. The organisms bearing the antigens are then engulfed by phagocytes. Binding of antibody and antigen may activate the complement system, which increases the efficiency of the phagocytes.
Cellular immunity is particularly important in the defence against viruses, some types of parasites that hide within cells, and, possibly, cancer cells. It involves 2 types of T-lymphocyte: helper cells, which play a role in the recognition of antigens and activate the killer cells (the 2nd type of T-lymphocyte), which destroy the cells that have been invaded.
Disorders of the immune system include immunodeficiency disorders and allergy, in which the immune system has an inappropriate response to usually innocuous antigens such as pollen.
In certain circumstances, such as after tissue transplants, immunosuppressant drugs are used to suppress the immune system and thus prevent rejection of the donor tissue as a foreign organism.... immune system
n. the process by which opsonins render foreign organisms or particles more attractive to *phagocytes by attaching to their outer surfaces and changing their physical and chemical composition. Phagocytic leucocytes express receptors for these opsonins and thereby engulf and digest foreign organisms or particles.... opsonization
(phago-) combining form denoting 1. eating. 2. phagocytes.... phag
n. (pl. pseudopodia) a temporary and constantly changing extension of the body of an amoeba or an amoeboid cell (see phagocyte). Pseudopodia engulf bacteria and other particles as food and are responsible for the movements of the cell.... pseudopodium
(RES) a community of cells – *phagocytes – spread throughout the body. It includes *macrophages and *monocytes. The RES is concerned with defence against microbial infection and with the removal of worn-out blood cells from the bloodstream. See also spleen.... reticuloendothelial system
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