CD34
Encyclopedia
CD34 molecule is a cluster of differentiation
molecule
present on certain cells within the human body. It is a cell surface glycoprotein
and functions as a cell-cell adhesion
factor. It may also mediate the attachment of stem cells to bone marrow
extracellular matrix or directly to stromal cell
s. CD34 is also the name for the human gene
that encodes the protein.
proteins that show expression on early hematopoietic and vascular-associated tissue . However little is known about its exact function.
CD34 is also an important adhesion molecule and is required for T cell
s to enter lymph node
s. It is expressed on lymph node endothelia
whereas the L-selectin
to which it binds is on the T cell.. Conversely, under other circumstances CD34 has been shown to act as molecular "Teflon" and block mast cell adhesion, or to facilitate opening of vascular lumens. Regardless of their mode of action, under all circumstances CD34 and its relatives, podocalyxin and endoglycan, have been shown to facilitate cell migration.
and bone marrow
as hematopoietic cells, a subset of mesenchymal stem cells, endothelial progenitor cell
s, endothelial cells of blood vessels but not lymphatics (except pleural lymphatics), mast cells, a sub-population dendritic cell
s (which are factor XIII
a negative) in the interstitium and around the adnexa
of dermis
of skin, as well as cells in soft tissue tumors like DFSP
, GIST
, PNST
s etc.
samples using immunomagnetic
or immunofluorescent
methods.
Antibodies are used to quantify and purify hematopoietic progenitor stem cells for research and for clinical bone marrow transplantation. However, counting CD34+ mononuclear cells may overestimate myeloid
blasts in bone marrow smears due to hematogones (B lymphocyte precursors) and CD34+ megakaryocytes.
Cells observed as CD34+ and CD38- are of an undifferentiated
, primitive form; i.e. they are pluripotential hemopoietic stem cell
s. Thus, because of their CD34+ expression, such undifferentiated cells can be sorted out.
In tumors, CD34 is found in alveolar soft part sarcoma
, preB-ALL (positive in 75%), AML (40%), AML-M7 (most), dermatofibrosarcoma protuberans
, gastrointestinal stromal tumor
s, giant cell fibroblastoma
, granulocytic sarcoma
, Kaposi’s sarcoma, liposarcoma
, malignant fibrous histiocytoma
, malignant peripheral nerve sheath tumors, mengingeal hemangiopericytoma
s, meningioma
s, neurofibroma
s, schwannoma
s, and papillary thyroid carcinoma.
A negative CD34 may exclude Ewing's sarcoma/PNET, myofibrosarcoma of the breast, and inflammatory myofibroblastic tumors of the stomach.
with CRKL
.. It also interacts
with L-selectin
, important in inflammation
.
Cluster of differentiation
The cluster of differentiation is a protocol used for the identification and investigation of cell surface molecules present on white blood cells, providing targets for immunophenotyping of cells...
molecule
Molecule
A molecule is an electrically neutral group of at least two atoms held together by covalent chemical bonds. Molecules are distinguished from ions by their electrical charge...
present on certain cells within the human body. It is a cell surface glycoprotein
Glycoprotein
Glycoproteins are proteins that contain oligosaccharide chains covalently attached to polypeptide side-chains. The carbohydrate is attached to the protein in a cotranslational or posttranslational modification. This process is known as glycosylation. In proteins that have segments extending...
and functions as a cell-cell adhesion
Adhesion
Adhesion is any attraction process between dissimilar molecular species that can potentially bring them in close contact. By contrast, cohesion takes place between similar molecules....
factor. It may also mediate the attachment of stem cells to bone marrow
Bone 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...
extracellular matrix or directly to stromal cell
Stromal cell
In cell biology, stromal cells are connective tissue cells of any organ, for example in the uterine mucosa , prostate, bone marrow, and the ovary. They are cells that support the function of the parenchymal cells of that organ...
s. CD34 is also the name for the human gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
that encodes the protein.
Function
The CD34 protein is a member of a family of single-pass transmembrane sialomucinMucin
Mucins are a family of high molecular weight, heavily glycosylated proteins produced by epithelial tissues in most metazoans. Mucins' key characteristic is their ability to form gels; therefore they are a key component in most gel-like secretions, serving functions from lubrication to cell...
proteins that show expression on early hematopoietic and vascular-associated tissue . However little is known about its exact function.
CD34 is also an important adhesion molecule and is required for T cell
T cell
T cells or T lymphocytes belong to a group of white blood cells known as lymphocytes, and play a central role in cell-mediated immunity. They can be distinguished from other lymphocytes, such as B cells and natural killer cells , by the presence of a T cell receptor on the cell surface. They are...
s to enter lymph node
Lymph node
A lymph node is a small ball or an oval-shaped organ of the immune system, distributed widely throughout the body including the armpit and stomach/gut and linked by lymphatic vessels. Lymph nodes are garrisons of B, T, and other immune cells. Lymph nodes are found all through the body, and act as...
s. It is expressed on lymph node endothelia
Endothelium
The endothelium is the thin layer of cells that lines the interior surface of blood vessels, forming an interface between circulating blood in the lumen and the rest of the vessel wall. These cells are called endothelial cells. Endothelial cells line the entire circulatory system, from the heart...
whereas the L-selectin
L-selectin
L-selectin, also known as CD62L, is a cell adhesion molecule found on leukocytes. It belongs to the selectin family of proteins, which recognize sialylated carbohydrate groups...
to which it binds is on the T cell.. Conversely, under other circumstances CD34 has been shown to act as molecular "Teflon" and block mast cell adhesion, or to facilitate opening of vascular lumens. Regardless of their mode of action, under all circumstances CD34 and its relatives, podocalyxin and endoglycan, have been shown to facilitate cell migration.
Tissue distribution
Cells expressing CD34 (CD34+ cell) are normally found in the umbilical cordUmbilical cord
In placental mammals, the umbilical cord is the connecting cord from the developing embryo or fetus to the placenta...
and bone marrow
Bone 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...
as hematopoietic cells, a subset of mesenchymal stem cells, endothelial progenitor cell
Endothelial progenitor cell
Endothelial progenitor cells are a population of rare cells that circulate in the blood with the ability to differentiate into endothelial cells, the cells that make up the lining of blood vessels. The process by which blood vessels are born de novo from endothelial progenitor cells is known as...
s, endothelial cells of blood vessels but not lymphatics (except pleural lymphatics), mast cells, a sub-population 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 (which are factor XIII
Factor XIII
Factor 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 negative) in the interstitium and around the adnexa
Adnexa
In anatomy, adnexa refers to the appendages of an organ. The term adnexa stems from a Latin word meaning appendages.More specifically, it can refer to:* Adnexa of eye * Adnexa of uterus...
of dermis
Dermis
The dermis is a layer of skin between the epidermis and subcutaneous tissues, and is composed of two layers, the papillary and reticular dermis...
of skin, as well as cells in soft tissue tumors like DFSP
Dermatofibrosarcoma protuberans
Dermatofibrosarcoma protuberans is a very rare tumor. It is a rare neoplasm of the dermis layer of the skin, and is classified as a sarcoma. There is only about 1 case per million per year. DFSP is a fibrosarcoma, more precisely a cutaneous soft tissue sarcoma...
, GIST
Gastrointestinal stromal tumor
A gastrointestinal stromal tumor is one of the most common mesenchymal tumors of the gastrointestinal tract...
, PNST
Malignant peripheral nerve sheath tumor
A malignant peripheral nerve sheath tumor is a form of cancer of the connective tissue surrounding nerves. Given its origin and behavior it is classified as a sarcoma...
s etc.
Clinical applications
CD34+ cells may be isolated from bloodBlood
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....
samples using immunomagnetic
Magnetic-activated cell sorting
Magnetic-activated cell sorting is a trademark name for a method for separation of various cell populations depending on their surface antigens . The term MACS is a registered trademark of Miltenyi Biotec....
or immunofluorescent
Flow cytometry
Flow cytometry is a technique for counting and examining microscopic particles, such as cells and chromosomes, by suspending them in a stream of fluid and passing them by an electronic detection apparatus. It allows simultaneous multiparametric analysis of the physical and/or chemical...
methods.
Antibodies are used to quantify and purify hematopoietic progenitor stem cells for research and for clinical bone marrow transplantation. However, counting CD34+ mononuclear cells may overestimate myeloid
Myeloid
The term myeloid suggests an origin in the bone marrow or spinal cord, or a resemblance to the marrow or spinal cord.In hematopoiesis, the term "myeloid cell" is used to describe any leukocyte that is not a lymphocyte...
blasts in bone marrow smears due to hematogones (B lymphocyte precursors) and CD34+ megakaryocytes.
Cells observed as CD34+ and CD38- are of an undifferentiated
Cellular differentiation
In developmental biology, cellular differentiation is the process by which a less specialized cell becomes a more specialized cell type. Differentiation occurs numerous times during the development of a multicellular organism as the organism changes from a simple zygote to a complex system of...
, primitive form; i.e. they are pluripotential hemopoietic stem cell
Pluripotential hemopoietic stem cell
Hematopoietic stem cells , also spelled Hæmatopoietic stem cells, are multipotent stem cells that give rise to all the blood cell types from the myeloid , and lymphoid lineages...
s. Thus, because of their CD34+ expression, such undifferentiated cells can be sorted out.
In tumors, CD34 is found in alveolar soft part sarcoma
Alveolar soft part sarcoma
Alveolar soft part sarcoma, abbreviated ASPS, is a very rare type of soft tissue sarcoma, that grows slowly and whose cell of origin is unknown.It arises mainly in children and young adults...
, preB-ALL (positive in 75%), AML (40%), AML-M7 (most), dermatofibrosarcoma protuberans
Dermatofibrosarcoma protuberans
Dermatofibrosarcoma protuberans is a very rare tumor. It is a rare neoplasm of the dermis layer of the skin, and is classified as a sarcoma. There is only about 1 case per million per year. DFSP is a fibrosarcoma, more precisely a cutaneous soft tissue sarcoma...
, gastrointestinal stromal tumor
Stromal tumor
A stromal tumor is a tumor that arises in the supporting connective tissue of an organ.-External links:* entry in the public domain NCI Dictionary of Cancer Terms...
s, giant cell fibroblastoma
Giant cell fibroblastoma
Giant-cell fibroblastoma is a rare type of soft tissue tumor marked by painless nodules in the dermis and subcutaneous tissue. These tumors may come back after surgery, but they do not spread to other parts of the body...
, granulocytic sarcoma
Granulocytic sarcoma
A myeloid sarcoma , is a solid tumor composed of immature white blood cells called myeloblasts...
, Kaposi’s sarcoma, liposarcoma
Liposarcoma
Liposarcoma is a malignant tumor that arises in fat cells in deep soft tissue, such as that inside the thigh or in the retroperitoneum.They are typically large bulky tumors which tend to have multiple smaller satellites extending beyond the main confines of the tumor.Liposarcomas, like all...
, malignant fibrous histiocytoma
Malignant fibrous histiocytoma
Pleomorphic undifferentiated sarcoma , also undifferentiated pleomorphic sarcoma and previously malignant fibrous histiocytoma , is a type of soft tissue sarcoma....
, malignant peripheral nerve sheath tumors, mengingeal hemangiopericytoma
Hemangiopericytoma
A hemangeopericytoma is a type of soft tissue sarcoma that originates in the pericytes in the walls of capillaries. When inside the nervous system, although not strictly a meningioma tumor, it is a meningeal tumor with an especially aggressive behavior.It was characterized in...
s, meningioma
Meningioma
The word meningioma was first used by Harvey Cushing in 1922 to describe a tumor originating from the meninges, the membranous layers surrounding the CNS ....
s, neurofibroma
Neurofibroma
A neurofibroma is a benign nerve sheath tumor in the peripheral nervous system. Usually found in individuals with neurofibromatosis type I , an autosomal dominant genetically-inherited disease, they can result in a range of symptoms from physical disfiguration and pain to cognitive disability...
s, schwannoma
Schwannoma
A schwannoma is a benign nerve sheath tumor composed of Schwann cells, which normally produce the insulating myelin sheath covering peripheral nerves....
s, and papillary thyroid carcinoma.
A negative CD34 may exclude Ewing's sarcoma/PNET, myofibrosarcoma of the breast, and inflammatory myofibroblastic tumors of the stomach.
Interactions
CD34 has been shown to interactProtein-protein interaction
Protein–protein interactions occur when two or more proteins bind together, often to carry out their biological function. Many of the most important molecular processes in the cell such as DNA replication are carried out by large molecular machines that are built from a large number of protein...
with CRKL
CRKL
Crk-like protein is a protein that in humans is encoded by the CRKL gene.CrkL together with Crk participates in the Reelin signaling cascade downstream of DAB1.-Interactions:...
.. It also interacts
Protein-protein interaction
Protein–protein interactions occur when two or more proteins bind together, often to carry out their biological function. Many of the most important molecular processes in the cell such as DNA replication are carried out by large molecular machines that are built from a large number of protein...
with L-selectin
L-selectin
L-selectin, also known as CD62L, is a cell adhesion molecule found on leukocytes. It belongs to the selectin family of proteins, which recognize sialylated carbohydrate groups...
, important in inflammation
Inflammation
Inflammation is part of the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. Inflammation is a protective attempt by the organism to remove the injurious stimuli and to initiate the healing process...
.