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Histiocyte
 
 
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A histiocyte is a cell
Cell (biology)

The cell is the structural and functional unit of all known Life organisms. It is the smallest unit of an organism that is classified as living, and is often called the building bricks of life....
 that is part of the mononuclear phagocytic system (also called reticuloendothelial system
Reticuloendothelial system

The reticuloendothelial system , part of the immune system, consists of the phagocytosis cells located in reticular connective tissue, primarily monocytes and macrophages....
 or lymphoreticular system). The mononuclear phagocytic system is part of the organism's immune system
Immune system

An immune system is a collection of biological processes within an organism that protects against disease by identifying and killing pathogens and tumour cells....
. The histiocyte is a tissue macrophage
Macrophage

Macrophages are white blood cells within tissues, produced by the division of monocytes. Human macrophages are about 21 micrometres in diameter....
 ("histo-" = "tissue", and "-cyte" = "cell").

iocytes are derived from the bone marrow
Bone marrow

Bone marrow is the flexible biological tissue found in the hollow interior of bones. In adults, marrow in large bones produces new blood cells....
 by multiplication from a stem cell
Stem cell

Stem cells are Cell found in most, if not all, multi-cellular organisms. They are characterized by the ability to renew themselves through Mitosis cell division and Cellular differentiation into a diverse range of specialized cell types....
. The derived cells migrate from the bone marrow to the blood
Blood

Blood is a specialized bodily fluid that delivers necessary substances to the body's Cell s ? such as nutrients and oxygen ? and transports waste products away from those same cells....
 as monocytes.






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Encyclopedia


A histiocyte is a cell
Cell (biology)

The cell is the structural and functional unit of all known Life organisms. It is the smallest unit of an organism that is classified as living, and is often called the building bricks of life....
 that is part of the mononuclear phagocytic system (also called reticuloendothelial system
Reticuloendothelial system

The reticuloendothelial system , part of the immune system, consists of the phagocytosis cells located in reticular connective tissue, primarily monocytes and macrophages....
 or lymphoreticular system). The mononuclear phagocytic system is part of the organism's immune system
Immune system

An immune system is a collection of biological processes within an organism that protects against disease by identifying and killing pathogens and tumour cells....
. The histiocyte is a tissue macrophage
Macrophage

Macrophages are white blood cells within tissues, produced by the division of monocytes. Human macrophages are about 21 micrometres in diameter....
 ("histo-" = "tissue", and "-cyte" = "cell").

Terminology

Histiocytes are derived from the bone marrow
Bone marrow

Bone marrow is the flexible biological tissue found in the hollow interior of bones. In adults, marrow in large bones produces new blood cells....
 by multiplication from a stem cell
Stem cell

Stem cells are Cell found in most, if not all, multi-cellular organisms. They are characterized by the ability to renew themselves through Mitosis cell division and Cellular differentiation into a diverse range of specialized cell types....
. The derived cells migrate from the bone marrow to the blood
Blood

Blood is a specialized bodily fluid that delivers necessary substances to the body's Cell s ? such as nutrients and oxygen ? and transports waste products away from those same cells....
 as 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).

However, the term "histiocyte" has been used for multiple purposes in the past, and some cells called "histocytes" don't appear to derive from monocytic-macrophage lines.

Some sources consider Langerhans cell
Langerhans cell

Langerhans cells are dendritic cells in the Epidermis , containing large granules called Birbeck granules. They are normally present in lymph nodes and other organs, including the stratum spinosum layer of the epidermis....
 derivatives to be histocytes. The Langerhans cell histiocytosis
Langerhans cell histiocytosis

Langerhans cell histiocytosis is a rare disease involving clonal proliferation of Langerhans cells, abnormal cell s deriving from bone marrow and capable of migrating from skin to lymph nodes....
 embeds this interpretation into its name.

Morphology and diversity

Histiocytes have common histological
Histology

Histology is the study of the anatomy of cell and tissue of plants and animals. It is performed by examining a thin slice of tissue under a light microscope or electron microscope....
 and immunophenotypical characteristics (demonstrated by immunostains
Immunostaining

Immunostaining is a general term in biochemistry that applies to any use of an antibody-based method to detect a specific protein in a sample. The term immunostaining was originally used to refer to the immunohistochemical staining of tissue sections, as first described by Albert Coons in 1941....
). Their cytoplasm
Cytoplasm

The cytoplasm is the part of a Cell that is enclosed within the plasma membrane. In eukaryote cells the cytoplasm contains organelles, such as mitochondrion, that are filled with liquid kept separate from the rest of the cytoplasm by biological membranes....
 is eosinophilic
Eosinophilic

Eosinophilic means loves eosin, and refers to the staining of certain Biological tissue, cell , or organelles after they have been washed with eosin, a dye....
 and contains variable amounts of lysosome
Lysosome

Lysosomes are organelles that contain digestive enzymes . Some biologists say they can only be found in animal cells, but there is new evidence that supports that they may exist in plant cells....
s. They bear membrane receptors for opsonin
Opsonin

An opsonin is any molecule that acts as a binding enhancer for the process of phagocytosis, for example, by coating the negatively-charged molecules on the membrane....
s, such as IgG and the fragment C3b of complement. They express LCAs (leucocyte common antigen
Leucocyte common antigen

Leucocyte common antigen family is a group of high molecular weight glycoproteins uniquely expressed on the surface of all leukocytes and their hemopoiesis progenitor cells....
s) CD45
CD45

In immunology, the CD45 antigen is a protein which was originally called leukocyte common antigen.The protein encoded by this gene is a member of the protein tyrosine phosphatase family....
, CD14
CD14

Cluster of differentiation 14 also known as CD14 is a human gene.The protein encoded by this gene is a component of the innate immune system....
, CD33
CD33

CD33 is a transmembrane receptor expressed on cells of myeloid lineage. It is usually considered myeloid-specific, but it can also be found on some lymphoid cells....
 and CD4
CD4

CD4 is a glycoprotein expressed on the surface of T helper cells, regulatory T cells, monocytes, macrophages, and dendritic cells. It was discovered in the late 1970s and was originally known as leu-3 and T4 before being named CD4 in 1984....
 (also expressed by T Helper Cells
T helper cell

T helper cells are a sub-group of lymphocytes that play an important role in establishing and maximizing the capabilities of the immune system....
).

Macrophages and dendritic cells

These histiocytes are part of the immune system by way of two distinct functions: phagocytosis
Phagocytosis

File:Phagocytosis in three steps.pngPhagocytosis is the cell process of Phagocytes and Protists of engulfing solid particles by the cell membrane to form an internal phagosome, which is a food vacuole, or pteroid....
 and antigen presentation
Antigen presentation

Antigen presentation is a process in the body's immune system by which macrophages, dendritic cells and other cell types capture antigens and then enable their recognition by T-cells....
. Phagocytosis is the main process of macrophage
Macrophage

Macrophages are white blood cells within tissues, produced by the division of monocytes. Human macrophages are about 21 micrometres in diameter....
s and antigen
Antigen

An antigen is a substance that prompts the generation of antibodies and can cause an immune response. The word originated from the notion that they can stimulate antibody generation....
 presentation the main property of dendritic cell
Dendritic cell

Dendritic cells are immune cells and form part of the mammalian immune system. Their main function is to process antigen material and present it on the surface to other cells of the immune system, thus functioning as antigen-presenting cells....
s (so called because of their star-like cytoplasmic processes).

Macrophage
Macrophage

Macrophages are white blood cells within tissues, produced by the division of monocytes. Human macrophages are about 21 micrometres in diameter....
s and dendritic cell
Dendritic cell

Dendritic cells are immune cells and form part of the mammalian immune system. Their main function is to process antigen material and present it on the surface to other cells of the immune system, thus functioning as antigen-presenting cells....
s 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
Morphology (biology)

The term morphology in biology refers to form, structure and configuration of an organism. This includes aspects of the outward appearance as well as the form and structure of the internal parts like bones and organs....
, phenotype
Phenotype

A phenotype is any observable characteristic or trait_ of an organism: such as its morphology , development, biochemical or physiological properties, or behavior....
 and size.

  • Macrophages are highly variable in size and morphology, their cytoplasm
    Cytoplasm

    The cytoplasm is the part of a Cell that is enclosed within the plasma membrane. In eukaryote cells the cytoplasm contains organelles, such as mitochondrion, that are filled with liquid kept separate from the rest of the cytoplasm by biological membranes....
     contains numerous acid phosphatase
    Acid phosphatase

    Acid phosphatase is a phosphatase, a type of enzyme, used to free attached phosphate groups from other molecules during digestion. It is basically a phosphomonoesterase....
     laden lysosomes - in relation to their specialised phagocytic function. They express CD68
    CD68

    CD68 is a glycoprotein which binds to low density lipoprotein.It is expressed on monocytes/macrophages.The mouse equivalent is called "macrosialin"....
    .


  • Dendritic cells have an indented (bean shaped) nucleus and cytoplasm with thin processes (dendritic). Their main activity is antigen presentation, they express Factor XIII
    Factor XIII

    Factor XIII or fibrin stabilizing factor is an enzyme of the coagulation that crosslinks fibrin. When thrombin has converted fibrinogen to fibrin, the latter forms a proteinaceous network in which every E-unit is crosslinked to only one D-unit....
    a, CD1
    CD1

    CD1 is a family of glycoproteins expressed on the surface of various human antigen-presenting cells. They are related to the class I MHC molecules, and are involved in the presentation of lipid antigens to T cells....
    c and Class II Human leukocyte antigen
    Human leukocyte antigen

    The human leukocyte antigen system is the name of the major histocompatibility complex in humans.The superlocus contains a large number of genes related to immune system function in humans....
    s.


Langerhans cells

A subset of cells differentiates into Langerhans cells; this maturation occurs in the squamous epithelium
Squamous epithelium

In anatomy, squamous epithelium is an epithelium characterised by its most superficial layer consisting of flat, scale-like cell called squamous cell....
, lymph nodes, spleen
Spleen

The spleen is an organ found in all vertebrate animals. In humans, the spleen is located in the abdomen of the body, where it functions in the destruction of redundant red blood cells, and holds a reservoir of blood....
, 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
Thymus

In human anatomy, the thymus is an organ located in the upper anterior portion of the Thoracic cavity just behind the sternum. The main function of the thymus is to provide an area for T lymphocyte maturation....
 gland). They also express S-100, and their nucleus contains tennis-racket like ultra-structural inclusions called Birbeck granules
Birbeck granules

Birbeck granules are rod shaped or "tennis-racket" cytoplasmic organelles with a central linear density and a striated appearance.Formation is induced by langerin....
.

Disorders

Histiocytoses
Histiocytosis

In medicine, histiocytosis is an excessive number of histiocytes, that is, an excessive number of tissue macrophages, and is typically used to refer to a group of rare diseases which share this as a characteristic....
 describe neoplasias where the proliferative cell is the histiocyte.

The most common histiocyte disorders are Langerhans' cell histiocytosis and haemophagocytic lymphohistiocytosis.

See also

  • Histiocytosis
    Histiocytosis

    In medicine, histiocytosis is an excessive number of histiocytes, that is, an excessive number of tissue macrophages, and is typically used to refer to a group of rare diseases which share this as a characteristic....