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CD23, also known as Fc epsilon RII, or FcεRII, is the "low-affinity"
receptor Receptor may refer to: *Sensory receptor, in physiology, any structure which, on receiving environmental stimuli, produces an informative nerve impulse *Receptor (biochemistry), in biochemistry, a protein molecule that receives and responds to a n ...
for IgE, an
antibody An antibody (Ab), also known as an immunoglobulin (Ig), is a large, Y-shaped protein used by the immune system to identify and neutralize foreign objects such as pathogenic bacteria and viruses. The antibody recognizes a unique molecule of t ...
isotype involved in
allergy Allergies, also known as allergic diseases, refer a number of conditions caused by the hypersensitivity of the immune system to typically harmless substances in the environment. These diseases include hay fever, food allergies, atopic derm ...
and resistance to
parasites Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson ha ...
, and is important in regulation of IgE levels. Unlike many of the antibody receptors, CD23 is a C-type
lectin Lectins are carbohydrate-binding proteins that are highly specific for sugar groups that are part of other molecules, so cause agglutination of particular cells or precipitation of glycoconjugates and polysaccharides. Lectins have a role in rec ...
. It is found on mature
B cells B cells, also known as B lymphocytes, are a type of white blood cell of the lymphocyte subtype. They function in the humoral immunity component of the adaptive immune system. B cells produce antibody molecules which may be either secreted o ...
, activated
macrophages Macrophages (abbreviated as M φ, MΦ or MP) ( el, large eaters, from Greek ''μακρός'' (') = large, ''φαγεῖν'' (') = to eat) are a type of white blood cell of the immune system that engulfs and digests pathogens, such as cancer ce ...
,
eosinophils Eosinophils, sometimes called eosinophiles or, less commonly, acidophils, are a variety of white blood cells (WBCs) and one of the immune system components responsible for combating multicellular parasites and certain infections in vertebrates. A ...
, follicular dendritic cells, and
platelets Platelets, also called thrombocytes (from Greek θρόμβος, "clot" and κύτος, "cell"), are a component of blood whose function (along with the coagulation factors) is to react to bleeding from blood vessel injury by clumping, thereby ...
. There are two forms of CD23: CD23a and CD23b. CD23a is present on follicular B cells, whereas CD23b requires IL-4 to be expressed on
T-cells A T cell is a type of lymphocyte. T cells are one of the important white blood cells of the immune system and play a central role in the adaptive immune response. T cells can be distinguished from other lymphocytes by the presence of a T-cell r ...
,
monocytes Monocytes are a type of leukocyte or white blood cell. They are the largest type of leukocyte in blood and can differentiate into macrophages and conventional dendritic cells. As a part of the vertebrate innate immune system monocytes also inf ...
,
Langerhans cells A Langerhans cell (LC) is a tissue-resident macrophage of the skin. These cells contain organelles called Birbeck granules. They are present in all layers of the epidermis and are most prominent in the stratum spinosum. They also occur in the ...
, eosinophils, and macrophages.


Function

CD23 is known to have a role of transportation in antibody feedback regulation. Antigens which enter the blood stream can be captured by antigen specific IgE antibodies. The IgE immune complexes that are formed bind to CD23 molecules on B cells, and are transported to the B cell follicles of the spleen. The antigen is then transferred from CD23+ B cells to CD11c+ antigen presenting cells. The CD11c+ cells in turn present the antigen to CD4+ T cells, which can lead to an enhanced antibody response.


Clinical significance

The allergen responsible in dust mite allergy Der p 1 is known to cleave CD23 from a cell’s surface. As CD23 is soluble, it can move freely and interact with cells in plasma. Recent studies have shown that increased levels of soluble CD23 cause the recruitment of non-sensitised B-cells in the presentation of antigen peptides to allergen-specific B-cells, therefore increasing the production of allergen specific IgE. IgE, in turn, is known to upregulate the cellular expression of CD23 and Fc epsilon RI (high-affinity IgE receptor). In
flow cytometry Flow cytometry (FC) is a technique used to detect and measure physical and chemical characteristics of a population of cells or particles. In this process, a sample containing cells or particles is suspended in a fluid and injected into the flow ...
, CD23 is helpful in the differentiation of chronic lymphocytic leukemia (CD23-positive) from mantle cell lymphoma (CD23-negative). CD23 can also be demonstrated in germinal centre follicular dendritic cells using
immunohistochemistry Immunohistochemistry (IHC) is the most common application of immunostaining. It involves the process of selectively identifying antigens (proteins) in cells of a tissue section by exploiting the principle of antibodies binding specifically to ant ...
but is minimally expressed by benign germinal center B cells. In contrast to neoplastic mantle cells (which are negative for CD23), the resting cells of physiologic mantle zone express CD23. Paradoxically,
Lymphoma Lymphoma is a group of blood and lymph tumors that develop from lymphocytes (a type of white blood cell). In current usage the name usually refers to just the cancerous versions rather than all such tumours. Signs and symptoms may include en ...
s arising from the mantle zone are generally negative for CD23, while most
B-cell chronic lymphomocytic leukaemia Chronic lymphocytic leukemia (CLL) is a type of cancer in which the bone marrow makes too many lymphocytes (a type of white blood cell). Early on, there are typically no symptoms. Later, non-painful lymph node swelling, feeling tired, fever, ni ...
s are positive, allowing immunohistochemistry to distinguish these conditions, which otherwise have a similar appearance. Reed–Sternberg cells are usually positive for CD23.


See also

*
Cluster of differentiation The cluster of differentiation (also known as cluster of designation or classification determinant and often abbreviated as CD) is a protocol used for the identification and investigation of cell surface molecules providing targets for immunophen ...
, a list of all the CD-numbered proteins


References


Further reading

* * * * * * * * * * * * * * * * * * * *


External links

*
PDBe-KB
provides an overview of all the structure information available in the PDB for Human Low affinity immunoglobulin epsilon Fc receptor {{Immune receptors Fc receptors Clusters of differentiation