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Agranulocytosis, also known as agranulosis or granulopenia, is an acute condition involving a severe and dangerous leukopenia, most commonly of neutrophils, and thus causing a neutropenia in the circulating blood. It is a severe lack of one major class of infection-fighting white blood cells. People with this condition are at very high risk of serious infections due to their suppressed immune system.
Eosinophils, sometimes called eosinophiles or, less commonly, acidophils, are a variety of white blood cells and one of the immune system components responsible for combating multicellular parasites and certain infections in vertebrates. Along with mast cells and basophils, they also control mechanisms associated with allergy and asthma. They are granulocytes that develop during hematopoiesis in the bone marrow before migrating into blood, after which they are terminally differentiated and do not multiply. They form about 2 to 3% of WBC's.
Neutrophils are the most abundant type of granulocytes and make up 40% to 70% of all white blood cells in humans. They form an essential part of the innate immune system, with their functions varying in different animals.
A lymphocyte is a type of white blood cell in the vertebrate immune system. Lymphocytes include natural killer cells, T cells, and B cells. They are the main type of cell found in lymph, which prompted the name "lymphocyte".
Basophils are a type of white blood cell. Basophils are the least common type of granulocyte, representing about 0.5% to 1% of circulating white blood cells. However, they are the largest type of granulocyte. They are responsible for inflammatory reactions during immune response, as well as in the formation of acute and chronic allergic diseases, including anaphylaxis, asthma, atopic dermatitis and hay fever. They also produce compounds that co-ordinate immune responses, including histamine and serotonin that induce inflammation, heparin that prevents blood clotting, although there are less than that found in mast cell granules. Mast cells were once thought to be basophils that migrated from blood into their resident tissues, but they are now known to be different types of cells.
Granulocytes are a category of white blood cells in the innate immune system characterized by the presence of specific granules in their cytoplasm. They are also called polymorphonuclear leukocytes because of the varying shape of the nucleus, which is usually lobed into three segments. This distinguishes them from the mononuclear agranulocytes. The term polymorphonuclear leukocyte often refers specifically to "neutrophil granulocytes", the most abundant of the granulocytes; the other types have lower numbers of lobes. Granulocytes are produced via granulopoiesis in the bone marrow.
Agranulocytes or nongranulocytes, also mononuclear leukocytes, are one of the two types of white blood cells, also known as leukocytes. The other type of white blood cells are known as granulocytes. Agranular cells are noted by the absence of granules in their cytoplasm, which distinguishes them from granulocytes. The two types of agranulocytes in the blood circulation are lymphocytes and monocytes, and these make up about 35% of the hematologic blood values.
An azurophilic granule is a cellular object readily stainable with a Romanowsky stain. In white blood cells and hyperchromatin, staining imparts a burgundy or merlot coloration. Neutrophils in particular are known for containing azurophils loaded with a wide variety of anti-microbial defensins that fuse with phagocytic vacuoles. Azurophils may contain myeloperoxidase, phospholipase A2, acid hydrolases, elastase, defensins, neutral serine proteases, bactericidal/permeability-increasing protein, lysozyme, cathepsin G, proteinase 3, and proteoglycans.
The innate immune system is one of the two main immunity strategies found in vertebrates. The innate immune system is an older evolutionary defense strategy, relatively speaking, and is the dominant immune system response found in plants, fungi, insects, and primitive multicellular organisms.
A Fc receptor is a protein found on the surface of certain cells – including, among others, B lymphocytes, follicular dendritic cells, natural killer cells, macrophages, neutrophils, eosinophils, basophils, human platelets, and mast cells – that contribute to the protective functions of the immune system. Its name is derived from its binding specificity for a part of an antibody known as the Fc region. Fc receptors bind to antibodies that are attached to infected cells or invading pathogens. Their activity stimulates phagocytic or cytotoxic cells to destroy microbes, or infected cells by antibody-mediated phagocytosis or antibody-dependent cell-mediated cytotoxicity. Some viruses such as flaviviruses use Fc receptors to help them infect cells, by a mechanism known as antibody-dependent enhancement of infection.
Antibody-dependent cellular cytotoxicity (ADCC), also referred to as antibody-dependent cell-mediated cytotoxicity, is a mechanism of cell-mediated immune defense whereby an effector cell of the immune system actively lyses a target cell, whose membrane-surface antigens have been bound by specific antibodies. It is one of the mechanisms through which antibodies, as part of the humoral immune response, can act to limit and contain infection.
Toxic granulation refers to dark coarse granules found in granulocytes, particularly neutrophils, in patients with inflammatory conditions.
Degranulation is a cellular process that releases antimicrobial cytotoxic or other molecules from secretory vesicles called granules found inside some cells. It is used by several different cells involved in the immune system, including granulocytes and mast cells. It is also used by certain lymphocytes such as natural killer (NK) cells and cytotoxic T cells, whose main purpose is to destroy invading microorganisms.
CD16, also known as FcγRIII, is a cluster of differentiation molecule found on the surface of natural killer cells, neutrophils, monocytes, and macrophages. CD16 has been identified as Fc receptors FcγRIIIa (CD16a) and FcγRIIIb (CD16b), which participate in signal transduction. The most well-researched membrane receptor implicated in triggering lysis by NK cells, CD16 is a molecule of the immunoglobulin superfamily (IgSF) involved in antibody-dependent cellular cytotoxicity (ADCC). It can be used to isolate populations of specific immune cells through fluorescent-activated cell sorting (FACS) or magnetic-activated cell sorting, using antibodies directed towards CD16.
A non-specific immune cell is an immune cell that responds to many antigens, not just one antigen. Non-specific immune cells function in the first line of defense against infection or injury. The innate immune system is always present at the site of infection and ready to fight the bacteria; it can also be referred to as the "natural" immune system. The cells of the innate immune system do not have specific responses and respond to each foreign invader using the same mechanism.
Neutrophil hypersegmentation can be defined as the presence of neutrophils whose nuclei have six or more lobes or the presence of more than 3% of neutrophils with at least five nuclear lobes. This is a clinical laboratory finding. It is visualized by drawing blood from a patient and viewing the blood smeared on a slide under a microscope. Normal neutrophils are uniform in size, with an apparent diameter of about 13 μm in a film. When stained, neutrophils have a segmented nucleus and pink/orange cytoplasm under light microscope. The majority of neutrophils have three nuclear segments (lobes) connected by tapering chromatin strands. A small percentage have four lobes, and occasionally five lobes may be seen. Up to 8% of circulating neutrophils are unsegmented.
In hematology, myelopoiesis in the broadest sense of the term is the production of bone marrow and of all cells that arise from it, namely, all blood cells. In a narrower sense, myelopoiesis also refers specifically to the regulated formation of myeloid leukocytes (myelocytes), including eosinophilic granulocytes, basophilic granulocytes, neutrophilic granulocytes, and monocytes.
White blood cells (WBCs), also called leukocytes or leucocytes, are the cells of the immune system that are involved in protecting the body against both infectious disease and foreign invaders. All white blood cells are produced and derived from multipotent cells in the bone marrow known as hematopoietic stem cells. Leukocytes are found throughout the body, including the blood and lymphatic system.
Eosinophil peroxidase is an enzyme found within the eosinophil granulocytes, innate immune cells of humans and mammals. This oxidoreductase protein is encoded by the gene EPX, expressed within these myeloid cells. EPO shares many similarities with its orthologous peroxidases, myeloperoxidase (MPO), lactoperoxidase (LPO), and thyroid peroxidase (TPO). The protein is concentrated in secretory granules within eosinophils. Eosinophil peroxidase is a heme peroxidase, its activities including the oxidation of halide ions to bacteriocidal reactive oxygen species, the cationic disruption of bacterial cell walls, and the post-translational modification of protein amino acid residues.
Neutrophil-specific granule deficiency is a rare congenital immunodeficiency characterized by an increased risk for pyogenic infections due to defective production of specific granules and gelatinase granules in patient neutrophils.
References
- ↑ "Definition: specific granule from Online Medical Dictionary".
- ↑ Okuda M, Takenaka T, Kawabori S, Ogami Y (July 1981). "Ultrastructural study of the specific granule of the human eosinophil". J. Submicrosc. Cytol. 13 (3): 465–71. PMID 7334549.
- ↑ John P. Greer; Maxwell Myer Wintrobe (1 December 2008). Wintrobe's clinical hematology. Lippincott Williams & Wilkins. pp. 173–. ISBN 978-0-7817-6507-7 . Retrieved 10 November 2010.
- ↑ Online Mendelian Inheritance in Man (OMIM): SPECIFIC GRANULE DEFICIENCY; SGD - 245480
