Histiocyte
Encyclopedia
A histiocyte is a cell
that is part of the mononuclear phagocyte system (also known as the reticuloendothelial system or lymphoreticular system). The mononuclear phagocytic system is part of the organism's immune system
. The histiocyte is a tissue
macrophage
or a dendritic cell
("histo-" = "tissue", and "-cyte" = "cell").
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 enter 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. (The term Histiocyte can also simply refer to a cell from monocyte origin outside the blood system, such as in a tissue (as in Rheumatoid Arthritis as pallasaiding histiocytes surrounding fibrinoid necrosis of rheumatoid nodules).
Some sources consider Langerhans cell
derivatives to be histocytes. The Langerhans cell histiocytosis
embeds this interpretation into its name.
and immunophenotypical characteristics (demonstrated by immunostains
). Their cytoplasm
is eosinophilic
and contains variable amounts of lysosome
s. They bear membrane receptors for opsonin
s, such as IgG and the fragment C3b of complement. They express LCAs (leucocyte common antigen
s) CD45
, CD14
, CD33
and CD4
(also expressed by T Helper Cells
).
. Phagocytosis is the main process of macrophage
s and antigen
presentation the main property of dendritic cell
s (so called because of their star-like cytoplasmic processes).
Macrophage
s and dendritic cell
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
, phenotype
and size.
, 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
.
describe neoplasias where the proliferative cell is the histiocyte.
The most common histiocyte disorders are Langerhans' cell histiocytosis and haemophagocytic lymphohistiocytosis.
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....
that is part of the mononuclear phagocyte system (also known as the reticuloendothelial system or lymphoreticular system). The mononuclear phagocytic system is part of the organism's immune system
Immune system
An immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own...
. The histiocyte is a tissue
Tissue (biology)
Tissue is a cellular organizational level intermediate between cells and a complete organism. A tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function. These are called tissues because of their identical functioning...
macrophage
Macrophage
Macrophages are cells produced by the differentiation of monocytes in tissues. Human macrophages are about in diameter. Monocytes and macrophages are phagocytes. Macrophages function in both non-specific defense as well as help initiate specific defense mechanisms of vertebrate animals...
or a dendritic cell
Dendritic cell
Dendritic cells are immune cells forming 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. That is, dendritic cells function as antigen-presenting cells...
("histo-" = "tissue", and "-cyte" = "cell").
Terminology
Histiocytes are derived from the bone marrowBone marrow
Bone marrow is the flexible tissue found in the interior of bones. In humans, bone marrow in large bones produces new blood cells. On average, bone marrow constitutes 4% of the total body mass of humans; in adults weighing 65 kg , bone marrow accounts for approximately 2.6 kg...
by multiplication from a stem cell
Stem cell
This article is about the cell type. For the medical therapy, see Stem Cell TreatmentsStem cells are biological cells found in all multicellular organisms, that can divide and differentiate into diverse specialized cell types and can self-renew to produce more stem cells...
. The derived cells migrate from the bone marrow to the blood
Blood
Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....
as monocytes. They circulate through the body and enter 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. (The term Histiocyte can also simply refer to a cell from monocyte origin outside the blood system, such as in a tissue (as in Rheumatoid Arthritis as pallasaiding histiocytes surrounding fibrinoid necrosis of rheumatoid nodules).
Some sources consider Langerhans cell
Langerhans cell
Langerhans cells are dendritic cells of the skin and mucosa, and contain large granules called Birbeck granules. They are present in all layers of the epidermis, but are most prominant in the stratum spinosum. They also occur in the papillary dermis, particularly around blood vessels, as well as...
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 cells 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 histologicalHistology
Histology is the study of the microscopic anatomy of cells and tissues of plants and animals. It is performed by examining cells and tissues commonly by sectioning and staining; followed by examination 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 a small gel-like substance residing between the cell membrane holding all the cell's internal sub-structures , except for the nucleus. All the contents of the cells of prokaryote organisms are contained within the cytoplasm...
is eosinophilic
Eosinophilic
Eosinophilic refers to the staining of certain tissues, cells, or organelles after they have been washed with eosin, a dye.Eosin is an acidic dye; thus, the structure being stained is basic....
and contains variable amounts of lysosome
Lysosome
thumb|350px|Schematic of typical animal cell, showing subcellular components. [[Organelle]]s: [[nucleoli]] [[cell nucleus|nucleus]] [[ribosomes]] [[vesicle |vesicle]] rough [[endoplasmic reticulum]]...
s. They bear membrane receptors for opsonin
Opsonin
An opsonin is any molecule that targets an antigen for an immune response. However, the term is usually used in reference to molecules that act as a binding enhancer for the process of phagocytosis, especially antibodies, which coat the negatively-charged molecules on the membrane. Molecules that...
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 hemopoietic progenitor cells....
s) CD45
CD45
Protein tyrosine phosphatase, receptor type, C also known as PTPRC is an enzyme that, in humans, is encoded by the PTPRC gene. PTPRC is also known as CD45 antigen , which was originally called leukocyte common antigen.- Function :The protein encoded by this gene is a member of the protein tyrosine...
, 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. CD14 exists in two forms. Either it is anchored into the membrane by a glycosylphosphatidylinositol tail or it appears in a soluble form...
, CD33
CD33
CD33 or Siglec-3 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.It binds sialic acids, therefore is a member of the SIGLEC family of lectins....
and CD4
CD4
CD4 is a glycoprotein expressed on the surface of T helper 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, a type of white blood cell, that play an important role in the immune system, particularly in the adaptive immune system. These cells have no cytotoxic or phagocytic activity; they cannot kill infected host cells or pathogens. Rather, they help other...
).
Macrophages and dendritic cells
These histiocytes are part of the immune system by way of two distinct functions: phagocytosis and antigen presentationAntigen 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 cells produced by the differentiation of monocytes in tissues. Human macrophages are about in diameter. Monocytes and macrophages are phagocytes. Macrophages function in both non-specific defense as well as help initiate specific defense mechanisms of vertebrate animals...
s and antigen
Antigen
An antigen is a foreign molecule that, when introduced into the body, triggers the production of an antibody by the immune system. The immune system will then kill or neutralize the antigen that is recognized as a foreign and potentially harmful invader. These invaders can be molecules such as...
presentation the main property of dendritic cell
Dendritic cell
Dendritic cells are immune cells forming 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. That is, dendritic cells function as antigen-presenting cells...
s (so called because of their star-like cytoplasmic processes).
Macrophage
Macrophage
Macrophages are cells produced by the differentiation of monocytes in tissues. Human macrophages are about in diameter. Monocytes and macrophages are phagocytes. Macrophages function in both non-specific defense as well as help initiate specific defense mechanisms of vertebrate animals...
s and dendritic cell
Dendritic cell
Dendritic cells are immune cells forming 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. That is, dendritic cells function 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
Tumor necrosis factors
Tumor necrosis factors refers to a group of cytokines family that can cause cell death . The first two members of the family to be identified were:...
and IL-4. The various categories of histocytes are distinguishable by their morphology
Morphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....
, phenotype
Phenotype
A phenotype is an organism's observable characteristics or traits: such as its morphology, development, biochemical or physiological properties, behavior, and products of behavior...
and size.
- Macrophages are highly variable in size and morphology, their cytoplasmCytoplasmThe cytoplasm is a small gel-like substance residing between the cell membrane holding all the cell's internal sub-structures , except for the nucleus. All the contents of the cells of prokaryote organisms are contained within the cytoplasm...
contains numerous acid phosphataseAcid phosphataseAcid 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 CD68CD68CD68 is a glycoprotein which binds to low density lipoprotein.It is expressed on monocytes/macrophages.The mouse equivalent is called "macrosialin".-Use in pathology:...
.
- Dendritic cells have an indented (bean shaped) nucleus and cytoplasm with thin processes (dendritic). Their main activity is antigen presentation, they express Factor XIIIFactor XIIIFactor XIII or fibrin stabilizing factor is an enzyme of the blood coagulation system that crosslinks fibrin.- Function :Factor XIII is a transglutaminase that circulates in the plasma as a heterotetramer of two catalytic A subunits and two carrier B subunits...
a, CD1CD1For the album by Throbbing Gristle, see 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 antigenHuman leukocyte antigenThe human leukocyte antigen system is the name of the major histocompatibility complex in humans. The super locus contains a large number of genes related to immune system function in humans. This group of genes resides on chromosome 6, and encodes cell-surface antigen-presenting proteins and...
s.
Langerhans cells
A subset of cells differentiates into Langerhans cells; this maturation occurs in the squamous epitheliumSquamous epithelium
In anatomy, squamous epithelium is an epithelium characterised by its most superficial layer consisting of flat, scale-like cells called squamous epithelial cells...
, lymph nodes, spleen
Spleen
The spleen is an organ found in virtually all vertebrate animals with important roles in regard to red blood cells and the immune system. In humans, it is located in the left upper quadrant of the abdomen. It removes old red blood cells and holds a reserve of blood in case of hemorrhagic shock...
, 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
The thymus is a specialized organ of the immune system. The thymus produces and "educates" T-lymphocytes , which are critical cells of the adaptive immune system....
gland). They also express S-100, and their nucleus contains tennis-racket like ultra-structural inclusions called Birbeck granules
Birbeck granules
Birbeck granules, also known as Birbeck bodies, are rod shaped or "tennis-racket" cytoplasmic organelles with a central linear density and a striated appearance...
.
Disorders
HistiocytosesHistiocytosis
In medicine, histiocytosis refers to an excessive number of histiocytes, , 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.