Fc fragment of IgE receptor II | Fc epsilon receptors | IUPHAR Guide to IMMUNOPHARMACOLOGY

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Fc fragment of IgE receptor II

Target id: 2935

Nomenclature: Fc fragment of IgE receptor II

Abbreviated Name: FCεRII

Family: Fc epsilon receptors

Annotation status:  image of a grey circle Awaiting annotation/under development. Please contact us if you can help with annotation.  » Email us

   GtoImmuPdb view: ON :     Fc fragment of IgE receptor II has curated data in GtoImmuPdb

Gene and Protein Information
Species TM AA Chromosomal Location Gene Symbol Gene Name Reference
Human 1 321 19p13.2 FCER2 Fc fragment of IgE receptor II
Mouse 1 331 8 A1.1; 8 1.92 cM Fcer2a Fc receptor, IgE, low affinity II, alpha polypeptide
Rat 1 331 12p12 Fcer2 Fc fragment of IgE 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
Fc receptor, IgE, low affinity II, alpha polypeptide | Fc receptor | CD23 | Fc epsilon RII | FcεRII
Database Links
Ensembl Gene
Entrez Gene
Human Protein Atlas
RefSeq Nucleotide
RefSeq Protein

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Ligand Sp. Action Affinity Units Reference
IgE heavy chain 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].


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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, T├ítrai 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 16/01/2019. IUPHAR/BPS Guide to PHARMACOLOGY, http://guidetoimmunopharmacology.org/GRAC/ObjectDisplayForward?objectId=2935.