A histiocyte is a cell that is part of the human
immune system. It is a tissue macrophage[MeshName|histiocyte] [eMedicineDictionary|Histiocyte] [ [http://wordnet.princeton.edu/perl/webwn?s=histiocyte WordNet Search - 3.0 ] ] ("histo-" = "tissue", and "-cyte" = "cell"). Some sources also consider Langerhans cellderivatives to be histocytes. [cite journal |author=Cline M |title=Histiocytes and histiocytosis |journal=Blood |volume=84 |issue=9 |pages=2840–53 |year=1994 |pmid=7524755]
All categories of histiocytes are derived from the
bone marrowby multiplication from a stem cell. The derived cells migrate from the bone marrow to the bloodas monocytes. They circulate through the body and stop in various organs where they undergo differentiation into histiocytes which are part of the mononuclear phagocytic system(MPS).
Histiocytes have common histological and immunophenotypical characteristics (demonstrated by immunostains). Their
cytoplasmis eosinophilic and contains variable amounts of lysosomes. They bear membrane receptors for opsonins, such as IgGand the fragment C3b of complement. They express LCAs ( leucocyte common antigens) CD45, CD14, CD33and CD4(also expressed by T Helper Cells). These histiocytes are part of the immune system by way of two distinct functions: phagocytosisand antigen presentation. Phagocytosis is the main process of macrophages and antigenpresentation the main property of dendritic cells (so called because of their star-like cytoplasmic processes). Macrophages and dendritic cells are derived from common bone marrow precursor cells that have undergone different differentiation (as histiocytes) under the influence of various environmental (tissue location) and growth factors such as GM-CSF, TNFand IL-4. The various categories of histocytes are distinguishable by their morphology, phenotypeand size.
Macrophages are highly variable in size and morphology, their
cytoplasmcontains numerous acid phosphataseladen lysosomes- in relation to their specialised phagocytic function. They express CD68.
Dendritic cells have an indented (bean shaped) nucleus and cytoplasm with thin processes (dendritic). Their main activity is antigen presentation, they express Factor XIIIa, CD1c and Class II
Human leukocyte antigens.
A subset of cells differentiates into
Langerhans cells; this maturation occurs in the squamous epithelium, lymph nodes, spleen, and bronchiolar epithelium. Langerhans cells are antigen presenting cells but have undergone further differentiation. Skin Langerhans cells express CD1a as do cortical thymocytes(cells of the cortex of the thymusgland). They also express S-100, and their nucleus contains tennis-racket like ultra-structural inclusions called Birbeck granules.
neoplasiaswhere the proliferative cell is the histiocyte.
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histiocyte — [ istjɔsit ] n. m. • 1917; du gr. histiôn « voile de navire, tenture, toile » et cyte ♦ Histol. Macrophage libre du tissu conjonctif assurant le remplacement des cellules par phagocytose. ● histiocyte nom masculin Cellule phagocyte (possédant la… … Encyclopédie Universelle
histiocyte — [his′tē ō sīt΄] n. 〚< Gr histion, web, dim. of histos (see HISTO ) + CYTE〛 a large macrophage, found in connective tissue, that participates in the body s reaction to infection and injury histiocytic [his′tē əsit′ik] adj. * * * … Universalium
histiocyte — [his′tē ō sīt΄] n. [< Gr histion, web, dim. of histos (see HISTO ) + CYTE] a large macrophage, found in connective tissue, that participates in the body s reaction to infection and injury histiocytic [his′tē əsit′ik] adj … English World dictionary
Histiocyte — Aussi appelé spongiocyte. C est une cellule de taille importante faisant partie du système immunitaire. C est un macrophage du tissu conjonctif (tissu de soutien, remplissage) qui dérive de la moelle osseuse. Au départ, les monocytes immatures… … Wikipédia en Français
histiocyte — noun Etymology: Greek histion web (diminutive of histos) + International Scientific Vocabulary cyte Date: 1924 a nonmotile macrophage of extravascular tissues and especially connective tissue • histiocytic adjective … New Collegiate Dictionary
histiocyte — noun a macrophage, derived from bone marrow, found in connective tissue … Wiktionary
Histiocyte — A type of white blood cell, also called a macrophage, that is created by the bone marrow. They usually stay in place, but when histiocytes are stimulated by infection or inflammation they become active, attacking bacteria and other foreign matter … Medical dictionary
histiocyte — n. macrophage, large white blood cell that absorbs and destroys foreign and infection causing organisms (Biology) … English contemporary dictionary
histiocyte — his·tio·cyte … English syllables
histiocyte — n. a fixed macrophage, i.e. one that is stationary within connective tissue … The new mediacal dictionary