cd23 cd23 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. fcer2available structurespdbortholog search: pdbe rcsb list of pdb id codes4ki1, 1t8c, 1t8d, 2h2r, 2h2t, 4ezm, 4g96, 4g9a, 4gi0, 4gj0, 4gjx, 4gk1, 4gko, 4j6j, 4j6k, 4j6l, 4j6m, 4j6n, 4j6p, 4j6qidentifiersaliasesfcer2, blast-2, cd23, cd23a, clec4j, fce2, igebf, fc fragment of ige receptor ii, fcerii, fc epsilon receptor iiexternal idsomim: 151445 mgi: 95497 homologene: 1517 genecards: fcer2 gene location (human)chr.chromosome 19 (human)band19p13.2start7,688,758 bpend7,702,146 bpgene location (mouse)chr.chromosome 8 (mouse)band8 a1.1|8 1.92 cmstart3,731,737 bpend3,744,175 bprna expression patternbgeehumanmouse (ortholog)top expressed inspleenlymph nodeappendixbloodmonocytebone marrow cellsthymusrectumgallbladdersubcutaneous adipose tissuetop expressed inspleenbloodsubcutaneous adipose tissuethymuswhite adipose tissuemorulamammary glandlungleft lungright lungmore reference expression databiogpsmore reference expression datagene ontologymolecular function ige binding integrin binding protein binding metal ion binding carbohydrate binding cellular component integral component of membrane extracellular region plasma membrane integral component of plasma membrane extracellular exosome external side of plasma membrane membrane biological process notch signaling pathway positive regulation of humoral immune response mediated by circulating immunoglobulin positive regulation of nitric-oxide synthase activity positive regulation of killing of cells of other organism positive regulation of nitric-oxide synthase biosynthetic process cytokine-mediated signaling pathway sources:amigo / quickgoorthologsspecieshumanmouseentrez220814128ensemblensg00000104921ensmusg00000005540uniprotp06734p20693refseq (mrna)nm_001207019nm_001220500nm_002002nm_001253737nm_001253739nm_001253743nm_001253745nm_001253746nm_001253747nm_013517refseq (protein)np_001193948np_001207429np_001993np_001240666np_001240668np_001240672np_001240674np_001240675np_001240676np_038545location (ucsc)chr 19: 7.69 – 7.7 mbchr 8: 3.73 – 3.74 mbpubmed searchwikidataview/edit humanview/edit mouse 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.