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Encyclopedia > Histiocyte

A Histiocyte is a cell that is part of the human immune system. All categories of Histiocytes are derived from the bone marrow by multiplication from a stem cell. The derived cells migrate from the bone marrow to the blood as monocytes. They circulate through the body and stop in various organs where they undergo differentiation into histiocytes which are part of the mononuclear phagocyte systems (MPS). Histiocytes have common histological and immunophenotypical characteristics (demonstrated by immunostains). Their cytoplasm is eosinophilic and contrains variable amounts of lysosomes. They bear membrane receptor Fc for IgG and the fragment C3 of complement. They express LCAs (leucocyte common antigens) CD45, CD14, CD33 and CD4 (T-Helper Cells). These histiocytes are part of the immunue system by way of two distinct functions: phagocytosis and antigen presentation. Phagocytosis is the main process of macrophages and antigen presentation 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, TNF and IL-4. The various categories of histocytes are distinguishable by their morphology, phenotype and size. Cells in culture, stained for keratin (red) and DNA (green) The cell is the structural and functional unit of all living organisms, sometimes called the building blocks of life. ... The immune system is the organ system that protects an organism from outside biological influences. ... Histology is the study of tissue sectioned as a thin slice, using a microscope. ... Immunostaining is a technique to apply coloured or fluorescent dyes to tissues in preparation for microscopic examination in histology. ... T cells are a subset of lymphocytes that play a large role in the immune response. ... Phagocytosis (literally, cell eating) is a form of endocytosis where large particles are enveloped by the cell membrane of a (usually larger) cell and internalized to form a phagosome, or food vacuole. ... Macrophages (Greek: big eaters) are cells found in tissues that are responsible for phagocytosis of pathogens, dead cells and cellular debris. ... Dendritic cells (DC) are immune cells and form part of the mammal immune system. ...


Macrophages are highly variable in size and morphology, their nucleus contains numerous acid phosphatase laden 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 HLA 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 thymus gland). They also express S-100, and their nucleus contains tennis-racket like ultra-structural inclusions called Birbeck granules. In human anatomy, the thymus is a ductless gland located in the upper anterior portion of the chest cavity. ...


Histiocytoses describe neoplasias where the proliferative cell is the histiocyte. There can be benign (reactive histocytoses), and malignant histiocytoses. With increasing understanding of histiocyte biology more rational classification of Histiocytoses was proposed by the Histiocyte society in 1985. The Langerhans Cell Histiocytoses form class I histiocytoses, non Langerhans cell histiocytoses form Class II, and malignant histiocytoses form Class III.


The WHO proposed more recently (increasingly being accepted) a classification of histiocytoses based on the presumed lineage of the histiocyte causing the lesion: Langerhans Cell, indeterminate cell/undifferentiated cell, dendrocyte and macrophage lineage.


WHO Classification of histiocytoses:


Presumed lineage of cell - Langerhans Cell - Histiocytosis X, Congenital self-healing reticulohistiocytosis.


Presumed lineage of cell - Indeterminate Cell - Indeterminate cell histiocytoma/histiocytosis, generalized eruptive histiocytoma, benign cephalic histiocytosis.


Presumed lineage of cell - Dendritic Cell - Disseminated dermal dendrocytoma, Xanthoma disseminatum, Juvenile/adult xanthogranuloma, Reticulohistiocytoma cutis, Multicentric reticulohistiocytosis, Necrobiotic xanthogranuloma, progressive nodular histiocytosis, hereditary progressive mucinous histiocytosis, familial histiocytic dermoarthritis, Erdheim-Chester disease.


Presumed lineage of Cell - Macrophage - Rosai Dorfman disease (Sinus Histiocytosis Massive Lymphadenopathy SHML syndrome), Haemophagocytic/Erythrophagocytic Syndromes (Familial and Sporadic types).


All these disease are histiocytoses, for example, Rosai Dorfman disease is a histocytosis of cells from a Macrophage cell lineage, and Histiocytosis X is a histiocytosis of a Langerhans cell lineage.


Reference: Cline MJ. Histiocytes and histiocytoses. Blood 1994;84:2840-2853


[[HISTIOCYTOSIS X.]]


Histiocytosis X is a clonal proliferation (thus neoplasia or malignant histiocytes) of cells of Langerhans cell lineage.


Three pattens of Histiocytosis X are recognised: Unifocal Langerhans Cell Histiocytosis (unifocal eosinophilic granuloma) , Multifocal Langerhans Cell Histiocytosis, Acute Disseminated Langerhans Cell Histiocytosis (Letterer-Siwe disease).


  Results from FactBites:
 
Histiocyte - Wikipedia, the free encyclopedia (609 words)
All categories of Histiocytes are derived from the bone marrow by multiplication from a stem cell.
Histiocytes have common histological and immunophenotypical characteristics (demonstrated by immunostains).
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, TNF and IL-4.
S1C5-Cell Types (1940 words)
In the blood, the progenitor of common histiocytes is the monocyte (a non-activated histiocyte).
The migratory "histiocytic" cells in such lesions, particularly in some lichenoid reactions, are elongated with scanty, pale cytoplasm, and have characteristic, thin, elongated, wavy nuclei with delicate nuclear chromatin.
Foamy histiocytes are characteristic of the reaction to leprae bacilli, particularly in the range of reactions near the lepromatous pole.
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