FCER2 (CD23): The Low-Affinity IgE Receptor and Its Role in Allergy and Immunity
A comprehensive biomedical overview of the FCER2 gene, encoding the CD23 protein, including its genomic context, expression patterns, associated diseases, and functional implications.
Gene Information Card
| Symbol | FCER2 |
|---|---|
| Full Name | Fc fragment of IgE receptor II |
| Gene Type | protein-coding |
| Chromosomal Location | 19p13.2 |
| NCBI Gene ID | 2208 ncbi.nlm.nih.gov/gene/2208 |
| Ensembl ID | ENSG00000104921 |
| UniProt ID | P06734 |
| OMIM ID | 151445 |
| HGNC ID | 3612 |
| Aliases | CD23, CD23A, FCE2, IGEB, BLAST-2, CLEC4J |
Description
The FCER2 gene encodes CD23, a type II transmembrane glycoprotein and C-type lectin that functions as the low-affinity receptor for immunoglobulin E (IgE). It is primarily expressed on mature B cells but can also be found on other immune cells, including monocytes, eosinophils, and platelets. CD23 exists in membrane-bound and soluble forms (sCD23), which are generated by proteolytic cleavage. This receptor plays a critical role in regulating IgE synthesis, antigen presentation, and B-cell growth and differentiation. It is involved in allergic responses and immune regulation, and its expression is modulated by cytokines such as IL-4 and IL-13.
Disease Associations
| Disease category | Pathophysiological mechanism | Genomic evidence |
|---|---|---|
| Allergic Asthma | FCER2 polymorphisms and altered sCD23 levels are associated with increased IgE production and airway inflammation, contributing to asthma susceptibility and severity. | ClinVar, PubMed |
| Atopic Dermatitis | Elevated sCD23 levels are observed in patients, correlating with disease severity and total serum IgE, suggesting a role in the pathogenesis of atopic dermatitis. | PubMed |
| Chronic Lymphocytic Leukemia (CLL) | CD23 is a diagnostic marker for CLL; its overexpression on malignant B cells is used for disease identification and monitoring. | PubMed, COSMIC |
| Common Variable Immunodeficiency (CVID) | Mutations in FCER2 have been identified in some CVID patients, potentially affecting B-cell function and antibody production. | ClinVar, PubMed |
Expression Profile
Tissue Expression
| Tissue | nTPM | level |
|---|---|---|
| Spleen | 12.4 | Medium |
| Lymph Node | 10.1 | Medium |
| Blood | 8.5 | Low |
| Bone Marrow | 5.2 | Low |
| Lung | 2.1 | Low |
Cell Line Expression
| Cell Line | nTPM | Notes |
|---|---|---|
| Ramos (Burkitt's lymphoma) | 45.2 | High expression; commonly used as a model for B-cell studies. |
| Daudi (Burkitt's lymphoma) | 38.7 | High expression; used in studies of B-cell differentiation. |
| HL-60 (Promyeloblast) | 3.4 | Low expression; can be induced by IL-4. |
| K-562 (Chronic myelogenous leukemia) | 1.2 | Very low expression; not typically expressed. |
| A549 (Lung carcinoma) | 0.8 | Very low expression; not typically expressed. |
Data source：Human Protein Atlas（proteinatlas.org）
Mutations & Variants
Hotspot Mutations
| Variant | Type | Frequency | Functional Description |
|---|---|---|---|
| rs28364072 (T>G) | SNP | ~20% (heterozygous) | Associated with increased sCD23 levels and risk for allergic asthma. |
| rs7249320 (C>T) | SNP | ~15% (heterozygous) | Linked to altered FCER2 expression and susceptibility to atopic dermatitis. |
| c.1012C>T (p.Arg338Ter) | Nonsense | Rare | Premature stop codon leading to a truncated, non-functional protein; associated with CVID. |
| c.754G>A (p.Gly252Ser) | Missense | Rare | Amino acid substitution in the lectin domain; may affect IgE binding affinity. |
Mutation functional classification
Loss of Function (LOF)
Loss-of-function mutations, such as the nonsense variant p.Arg338Ter, result in a truncated CD23 protein that cannot be expressed on the cell surface or bind IgE effectively. This leads to impaired regulation of IgE synthesis and B-cell function, contributing to immunodeficiencies like CVID.
Gain of Function (GOF)
Gain-of-function mutations are not well-documented for FCER2. However, certain SNPs (e.g., rs28364072) are associated with increased production of soluble CD23 (sCD23), which may be considered a functional gain in terms of sCD23-mediated signaling, potentially exacerbating allergic inflammation.
Dominant Negative (DN)
No clear dominant-negative mutations have been reported for FCER2. Since CD23 functions as a trimer on the cell surface, a mutant monomer could theoretically interfere with trimer formation, but this has not been experimentally demonstrated in clinical studies.
View complete mutation data：
Gene Ontology (GO)
Pathways
• IgE mediated immune response
• B cell receptor signaling pathway
• Cytokine-cytokine receptor interaction
• Hematopoietic cell lineage
Protein Summary
CD23 is a 45 kDa type II transmembrane protein that forms homotrimers on the cell surface. It consists of a short N-terminal cytoplasmic domain, a single transmembrane region, and a large C-terminal extracellular domain containing a C-type lectin-like domain responsible for IgE binding. The protein is cleaved by ADAM metalloproteases to release soluble CD23 (sCD23), which retains IgE-binding activity. CD23 regulates IgE production by capturing IgE-antigen complexes and presenting them to T cells, thereby modulating the allergic response. It also plays a role in B-cell survival and differentiation.
Related Services
Related Products
| Product name | Cat.No. | Species | Gene ID | |
|---|---|---|---|---|
| FCER2 Knockout HEK293 Cell Line | EDJ-KQ3797 | Human | 2208 | Details Get a Quote |
| FCER2 Knockout HeLa Cell Line | EDJ-KQ53206 | Human | 2208 | Details Get a Quote |
| FCER2 Knockout A-549 Cell Line | EDJ-KQ61687 | Human | 2208 | Details Get a Quote |
| FCER2 Knockout HCT 116 Cell Line | EDJ-KQ70173 | Human | 2208 | Details Get a Quote |
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