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Fc fragment of IgE receptor II

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Immunopharmacology Ligand target has curated data in GtoImmuPdb

Target id: 2935

Nomenclature: Fc fragment of IgE receptor II

Abbreviated Name: FCεRII

Family: Fc epsilon receptors

Gene and Protein Information Click here for help
Species TM AA Chromosomal Location Gene Symbol Gene Name Reference
Human 1 321 19p13.2 FCER2 Fc epsilon receptor II
Mouse 1 331 8 1.92 cM Fcer2a Fc receptor, IgE, low affinity II, alpha polypeptide
Rat 1 331 12p12 Fcer2 Fc epsilon receptor II
Gene and Protein Information Comments
There are three transcript variants of the human FCER2 gene, giving rise to two protein isoforms: FCER2a (321aa) and FCERb (320aa). We provide details for the longest protein isoform from the mouse gene, but others have been detected. Like the human gene, the rat gene produces two protein isoforms: isoform a (331aa) and isoform b (310aa).
Previous and Unofficial Names Click here for help
Fc receptor, IgE, low affinity II, alpha polypeptide | Fc receptor | CD23 | Fc epsilon RII | FcεRII
Database Links Click here for help
ChEMBL Target
Ensembl Gene
Entrez Gene
Human Protein Atlas
RefSeq Nucleotide
RefSeq Protein

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Ligand Sp. Action Value Parameter Reference
IgE heavy chain Peptide Primary target of this compound Click here for species-specific activity table Immunopharmacology Ligand Hs Binding 7.0 pKd
pKd 7.0 (Kd 1x10-7 M)
Antibody Comments
A monoclonal antibody targeting FCER2 (CD23) was developed by IDEC Pharmaceuticals as an immunomodulating therapeutic for the potential treament of allergic asthma [5-6] and as a treatment for chronic lymphocytic leukemia (CLL). Development in both indications was terminated due to failure to meet primary endpoints in clinical trials [1,3].
Immunopharmacology Comments
FcεRII (CD23) is the low-affinity receptor for immunoglobulin E (IgE) with a Kd > 100nM. This protein is a C-type lectin found on mature B cells, activated macrophages, eosinophils, follicular dendritic cells, and platelets. It has no structural similarities with other Fc receptors. FcεRII has functions as both a membrane-bound and as a soluble receptor [4,7]. Functions include regulation of B cell growth and differentiation and of the effector phase of IgE-mediated immunity. It is also involved in regulating IgE production [7].

FcεRII is used as an immunohistological diagnostic marker to differentiate chronic lymphocytic leukemia (CLL) from mantle cell leukemia [2], as most B-cell CLLs and low-grade B-cell lymphomas are FcεRII +ve, whereas lymphomas arising from the mantle zone are generally FcεRII -ve.

FcεRII has been investigated as a clinical drug target the potential treament of allergic asthma [5-6] and as a treatment for chronic lymphocytic leukemia (CLL). Development in both indications was terminated due to failure to meet primary endpoints in clinical trials [1,3]. The agent tested in these trials was lumiliximab (IDEC-152, a chimeric Macaca irus- human monoclonal antibody) developed by IDEC Pharmaceuticals.
Cell Type Associations
Immuno Cell Type:  Granulocytes
Cell Ontology Term:   eosinophil (CL:0000771)
Immuno Cell Type:  B cells
Cell Ontology Term:   B cell (CL:0000236)
Immuno Cell Type:  Macrophages & monocytes
Comment:  Langerhans cells
Immuno Process Associations
Immuno Process:  Cytokine production & signalling
Immuno Process:  T cell (activation)
Immuno Process:  B cell (activation)
Immuno Process:  Immune regulation


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1. Awan FT, Hillmen P, Hellmann A, Robak T, Hughes SG, Trone D, Shannon M, Flinn IW, Byrd JC, LUCID trial investigators. (2014) A randomized, open-label, multicentre, phase 2/3 study to evaluate the safety and efficacy of lumiliximab in combination with fludarabine, cyclophosphamide and rituximab versus fludarabine, cyclophosphamide and rituximab alone in subjects with relapsed chronic lymphocytic leukaemia. Br J Haematol, 167 (4): 466-77. [PMID:25130401]

2. Barna G, Reiniger L, Tátrai P, Kopper L, Matolcsy A. (2008) The cut-off levels of CD23 expression in the differential diagnosis of MCL and CLL. Hematol Oncol, 26 (3): 167-70. [PMID:18381689]

3. Byrd JC, Kipps TJ, Flinn IW, Castro J, Lin TS, Wierda W, Heerema N, Woodworth J, Hughes S, Tangri S et al.. (2010) Phase 1/2 study of lumiliximab combined with fludarabine, cyclophosphamide, and rituximab in patients with relapsed or refractory chronic lymphocytic leukemia. Blood, 115 (3): 489-95. [PMID:19843887]

4. Kikutani H, Yokota A, Uchibayashi N, Yukawa K, Tanaka T, Sugiyama K, Barsumian EL, Suemura M, Kishimoto T. (1989) Structure and function of Fc epsilon receptor II (Fc epsilon RII/CD23): a point of contact between the effector phase of allergy and B cell differentiation. Ciba Found Symp, 147: 23-31; discussion 31-5. [PMID:2695308]

5. Poole JA, Meng J, Reff M, Spellman MC, Rosenwasser LJ. (2005) Anti-CD23 monoclonal antibody, lumiliximab, inhibited allergen-induced responses in antigen-presenting cells and T cells from atopic subjects. J Allergy Clin Immunol, 116 (4): 780-8. [PMID:16210051]

6. Rosenwasser LJ, Meng J. (2005) Anti-CD23. Clin Rev Allergy Immunol, 29 (1): 61-72. [PMID:16222084]

7. Yokota A, Kikutani H, Tanaka T, Sato R, Barsumian EL, Suemura M, Kishimoto T. (1988) 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. [PMID:2972386]

How to cite this page

Fc epsilon receptors: Fc fragment of IgE receptor II. Last modified on 08/03/2018. Accessed on 12/07/2024. IUPHAR/BPS Guide to PHARMACOLOGY,