Biology:CD23

Short description: Low-affinity" receptor for IgE

Generic protein structure example

CD23, also known as Fc epsilon RII, or FcεRII, is the "low-affinity" receptor for IgE, an antibody isotype involved in allergy and resistance to parasites, and is important in regulation of IgE levels. Unlike many of the antibody receptors, CD23 is a C-type lectin. It is found on mature B cells, activated macrophages, eosinophils, follicular dendritic cells, and platelets.

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, monocytes, Langerhans cells, 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).

Patterns of CD23 (and CD21) expression by the follicular dendritic cells in follicular lymphoma.

In flow cytometry, 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 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, Lymphomas arising from the mantle zone are generally negative for CD23, while most B-cell chronic lymphomocytic leukaemias 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, a list of all the CD-numbered proteins

Further reading

• "CD23 (the low-affinity IgE receptor) as a C-type lectin: a multidomain and multifunctional molecule". Cellular and Molecular Life Sciences 59 (4): 648–64. Apr 2002. doi:10.1007/s00018-002-8455-1. PMID 12022472. 
• "Regulation of CD23 expression by Notch2 in B-cell chronic lymphocytic leukemia". Leukemia & Lymphoma 46 (2): 157–65. Feb 2005. doi:10.1080/10428190400010742. PMID 15621797. 
• "Induction of Fc epsilon RII/CD23 on PHA-activated human peripheral blood T lymphocytes and the association of Fyn tyrosine kinase with Fc epsilon RII/CD23". Research in Immunology 143 (4): 422–5. May 1992. doi:10.1016/S0923-2494(05)80075-6. PMID 1387715. 
• "Partial characterization of natural and recombinant human soluble CD23". The Biochemical Journal 286 ( Pt 3) (Pt 3): 819–24. Sep 1992. doi:10.1042/bj2860819. PMID 1417742. 
• "Induction of Fc epsilon RII/CD23 on PHA-activated human peripheral blood T lymphocytes and association of fyn tyrosine kinase with Fc epsilon RII/CD23". International Journal of Tissue Reactions 14 (3): 121–30. 1992. PMID 1446976. 
• "Fyn tyrosine kinase associated with Fc epsilon RII/CD23: possible multiple roles in lymphocyte activation". Proceedings of the National Academy of Sciences of the United States of America 88 (20): 9132–5. Oct 1991. doi:10.1073/pnas.88.20.9132. PMID 1717997. Bibcode: 1991PNAS...88.9132S. 
• "Molecular structure and expression of the murine lymphocyte low-affinity receptor for IgE (Fc epsilon RII)". Proceedings of the National Academy of Sciences of the United States of America 86 (19): 7566–70. Oct 1989. doi:10.1073/pnas.86.19.7566. PMID 2529542. 
• "Molecular structure of human lymphocyte receptor for immunoglobulin E". Cell 47 (5): 657–65. Dec 1986. doi:10.1016/0092-8674(86)90508-8. PMID 2877743. 
• "Human lymphocyte Fc receptor for IgE: sequence homology of its cloned cDNA with animal lectins". Proceedings of the National Academy of Sciences of the United States of America 84 (3): 819–23. Feb 1987. doi:10.1073/pnas.84.3.819. PMID 2949326. Bibcode: 1987PNAS...84..819I. 
• "Two species of human Fc epsilon receptor II (Fc epsilon RII/CD23): tissue-specific and IL-4-specific regulation of gene expression". Cell 55 (4): 611–8. Nov 1988. doi:10.1016/0092-8674(88)90219-X. PMID 2972386. 
• "Cloning and expression of the cDNA coding for a human lymphocyte IgE receptor". The EMBO Journal 6 (1): 109–14. Jan 1987. doi:10.1002/j.1460-2075.1987.tb04726.x. PMID 3034567. 
• "CD23 interacts with a new functional extracytoplasmic domain involving N-linked oligosaccharides on CD21". Journal of Immunology 152 (12): 5806–13. Jun 1994. doi:10.4049/jimmunol.152.12.5806. PMID 7515913. 
• "CD23 regulates monocyte activation through a novel interaction with the adhesion molecules CD11b-CD18 and CD11c-CD18". Immunity 3 (1): 119–25. Jul 1995. doi:10.1016/1074-7613(95)90164-7. PMID 7621072. 
• "Oligo-capping: a simple method to replace the cap structure of eukaryotic mRNAs with oligoribonucleotides". Gene 138 (1–2): 171–4. Jan 1994. doi:10.1016/0378-1119(94)90802-8. PMID 8125298. 
• "Modeling of the lectin-homology domains of the human and murine low-affinity Fc epsilon receptor (Fc epsilon RII/CD23)". Receptor 3 (4): 325–41. 1994. PMID 8142907. 
• "Fluorescence in situ hybridization mapping of human chromosome 19: cytogenetic band location of 540 cosmids and 70 genes or DNA markers". Genomics 15 (1): 133–45. Jan 1993. doi:10.1006/geno.1993.1021. PMID 8432525. https://zenodo.org/record/1229582. 
• "HIV-gp 160-induced T cell-dependent B cell differentiation. Role of T cell-B cell activation molecule and IL-6". Journal of Immunology 150 (6): 2478–86. Mar 1993. doi:10.4049/jimmunol.150.6.2478. PMID 8450224. 
• "Genetic markers on chromosome 19p and prenatal diagnosis of HLA class II-deficient combined immunodeficiency". Pediatric Research 38 (5): 812–6. Nov 1995. doi:10.1203/00006450-199511000-00029. PMID 8552454. 
• "Structure-based modeling of the ligand binding domain of the human cell surface receptor CD23 and comparison of two independently derived molecular models". Protein Science 5 (2): 240–7. Feb 1996. doi:10.1002/pro.5560050207. PMID 8745401. 
• "Human lymphocytes shed a soluble form of CD21 (the C3dg/Epstein-Barr virus receptor, CR2) that binds iC3b and CD23". European Journal of Immunology 26 (7): 1497–503. Jul 1996. doi:10.1002/eji.1830260714. PMID 8766552. 

External links

• Human FCER2 genome location and FCER2 gene details page in the UCSC Genome Browser.
• PDBe-KB provides an overview of all the structure information available in the PDB for Human Low affinity immunoglobulin epsilon Fc receptor