CD1 (

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 ...

1) is a family of

glycoproteins Glycoproteins are proteins which contain oligosaccharide chains covalently attached to amino acid side-chains. The carbohydrate is attached to the protein in a cotranslational or posttranslational modification. This process is known as glycosy ...

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 Lipids are a broad group of naturally-occurring molecules which includes fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids includ ...

antigens to

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 re ...

. However their precise function is unknown.

Types

CD1 glycoproteins can be classified primarily into two groups which differ in their lipid anchoring. * CD1a, CD1b and CD1c (

group 1 CD1 CD1 (cluster of differentiation 1) 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 ...

molecules) are expressed on cells specialized for antigen presentation. *

CD1d CD1D is the human gene that encodes the protein CD1d, a member of the CD1 (cluster of differentiation 1) family of glycoproteins expressed on the surface of various human antigen-presenting cells. They are non-classical MHC proteins, related to ...

(group 2 CD1) is expressed in a wider variety of cells. CD1e is an intermediate form, expressed intracellularly, the role of which is currently unclear.

In humans

Group 1

Group 1 CD1 CD1 (cluster of differentiation 1) 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 ...

molecules have been shown to present foreign lipid antigens, and specifically a number of mycobacterial cell wall components, to CD1-specific T cells.

Group 2

The natural antigens of group 2 CD1 are not well characterized, but a synthetic glycolipid, alpha-galactosylceramide, originally isolated from a compound found in a marine sponge, has strong biologic activity. Group 2 CD1 molecules activate a group of T cells, known as

Natural killer T cell Natural killer T (NKT) cells are a heterogeneous group of T cells that share properties of both T cells and natural killer cells. Many of these cells recognize the non-polymorphic CD1d molecule, an antigen-presenting molecule that binds self an ...

s because of their expression of NK surface markers such as

CD161 Killer cell lectin-like receptor subfamily B, member 1, also known as KLRB1, NKR-P1A or CD161 (cluster of differentiation 161), is a human gene. Function Natural killer (NK) cells are lymphocytes that mediate cytotoxicity and secrete cytokines ...

. Natural Killer T (NKT) cells are activated by CD1d-presented antigens, and rapidly produce Th1 and Th2 cytokines, typically represented by interferon-gamma and IL-4 production. The group 2 (CD1d) ligand alpha-galactosylceramide is currently in phase I clinical trials for the treatment of advanced non-hematologic cancers.

Diagnostic relevance

CD1 antigens are expressed on cortical

thymocyte A Thymocyte is an immune cell present in the thymus, before it undergoes transformation into a T cell. Thymocytes are produced as stem cells in the bone marrow and reach the thymus via the blood. Thymopoiesis describes the process which turns thymo ...

s, but not on mature T cells. This often remains true in

neoplastic A neoplasm () is a type of abnormal and excessive growth of tissue. The process that occurs to form or produce a neoplasm is called neoplasia. The growth of a neoplasm is uncoordinated with that of the normal surrounding tissue, and persists ...

cells from these populations, so that the presence of CD1 antigens can be used in diagnostic immunohistochemistry to identify some

thymoma A thymoma is a tumor originating from the epithelial cells of the thymus that is considered a rare malignancy. Thymomas are frequently associated with neuromuscular disorders such as myasthenia gravis; thymoma is found in 20% of patients with m ...

s and malignancies arising from T cell precursors. CD1a, in particular, is a specific marker for

Langerhans cell 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 ...

s, and can therefore also be used in the diagnosis of

Langerhans cell histiocytosis Langerhans cell histiocytosis (LCH) is an abnormal clonal proliferation of Langerhans cells, abnormal cells deriving from bone marrow and capable of migrating from skin to lymph nodes. Symptoms range from isolated bone lesions to multisystem d ...

. Other conditions that may show CD1 positivity include

myeloid leukaemia Myeloid leukemia is a type of leukemia affecting myeloid tissue. Types include: * Acute myeloid leukemia * Chronic myelogenous leukemia * Acute megakaryoblastic leukemia * Blastic plasmacytoid dendritic cell neoplasm See also * Hematological m ...

and some B cell

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 enla ...

In cows and mice

Mice lack the group 1 CD1 molecules, and instead have 2 copies of

. Thus, mice have been used extensively to characterize the role of CD1d and CD1d-dependent

NKT cell The New Kadampa Tradition – International Kadampa Buddhist Union (NKT—IKBU) is a global Buddhist new religious movement founded by Kelsang Gyatso in England in 1991. In 2003 the words "International Kadampa Buddhist Union" (IKBU) were a ...

s in a variety of disease models. It has recently been shown that

cows Cattle (''Bos taurus'') are large, domesticated, cloven-hooved, herbivores. They are a prominent modern member of the subfamily Bovinae and the most widespread species of the genus ''Bos''. Adult females are referred to as cows and adult mal ...

lack the group 2 CD1 molecules, and have an expanded set of group 1 CD1 molecules. Because of this and the fact that cows are a natural host of

Mycobacterium bovis ''Mycobacterium bovis'' is a slow-growing (16- to 20-hour generation time) aerobic bacterium and the causative agent of tuberculosis in cattle (known as bovine TB). It is related to '' Mycobacterium tuberculosis'', the bacterium which causes tub ...

, a pathogen in humans as well, it is hoped that studying cows will yield insights into the group 1 CD1 antigen-presenting system.

References

External links

*
Mouse CD Antigen Chart

{{Clusters of differentiation Clusters of differentiation