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Published on: November 1, 2014
Molecular characterization of the low-affinity IgE receptor Fc epsilonRII/CD23 expressed by human eosinophils
S G Abdelilah1, L Bouchaïb, M Morita
1INSERM U167, Institut Pasteur, Lille, France.
Insights
Human eosinophils express the low-affinity IgE receptor (Fc epsilonRII/CD23), identical to the molecule on B cells. Both CD23 isoforms a and b are synthesized by eosinophils, confirmed by molecular cloning data.
Area of Science:
- Immunology
- Molecular Biology
- Cell Biology
Background:
- CD23/Fc epsilonRII, the low-affinity IgE receptor, influences B cell activation, proliferation, antigen presentation, and IgE synthesis.
- Initially thought to be restricted to B lymphocytes and macrophages, CD23 expression is now known to occur in a wider range of cells.
- Previous studies suggested potential biological functions of Fc epsilonRII/CD23 in human eosinophils, but lacked molecular cloning evidence.
Purpose of the Study:
- To definitively confirm the expression and molecular identity of the low-affinity IgE receptor (Fc epsilonRII/CD23) in human eosinophils.
- To investigate the presence and isoforms (a and b) of CD23 mRNA and protein in eosinophils.
- To analyze CD23 expression in both normal and hypereosinophilic conditions, including eosinophilic leukemia cell lines.
Main Methods:
- In situ hybridization to detect CD23 mRNA in eosinophils.
- RT-PCR analysis of human eosinophil cDNA and eosinophilic leukemia cell lines (EoL-3) to identify CD23 sequences.
- In situ RT-PCR to confirm mRNA localization within eosinophils.
- Immunocytochemistry to assess differential expression of Fc epsilonRII/CD23 and Fc epsilonRI on eosinophil subpopulations.
Main Results:
- In situ hybridization confirmed CD23 mRNA expression in human eosinophils.
- RT-PCR analysis revealed CD23 sequences in eosinophil cDNA, homologous to CD23 a and b.
- Both CD23 a and b isoforms were detected by RT-PCR in eosinophils from hypereosinophilic patients and the EoL-3 cell line.
- Immunocytochemistry demonstrated differential expression of Fc epsilonRII/CD23 and Fc epsilonRI, with Fc epsilonRII/CD23 predominantly in hypodense eosinophils.
Conclusions:
- Provides definitive molecular evidence that human eosinophils synthesize Fc epsilonRII/CD23, identical to the B cell molecule.
- Confirms that both CD23 a and b isoforms are expressed by human eosinophils.
- Highlights the potential role of Fc epsilonRII/CD23 in eosinophil subpopulations, particularly the hypodense fraction.
Abstract:
CD23/Fc epsilonRII, the low-affinity receptor for IgE, is a pluripotent molecule with pleiotropic effects on cell activation and proliferation, antigen presentation and IgE synthesis. Initial investigations have suggested that CD23 expression was restricted to B lymphocytes and macrophages, but a much wider cell distribution is now acknowledged. Despite experimental evidence suggesting that human eosinophils could express the low-affinity IgE receptor Fc epsilonRII/CD23 with biological functions, no molecular cloning data have been reported until now. Whereas in situ hybridization confirmed the expression of CD23 mRNA in eosinophils, RT-PCR analysis of human eosinophil cDNA derived from a cDNA library revealed the presence of CD23, totally homologous with the CD23 a and b sequences. Eosinophils from different hypereosinophilic patients as well as the eosinophilic leukemia cell line EoL-3, analyzed by RT-PCR, expressed both CD23 a and b isoforms. In situ RT-PCR confirmed that mRNA corresponding to CD23 a and b isoforms was detected in human eosinophils. Finally, immunocytochemistry allowed us to show a differential expression of Fc epsilonRII/CD23 and Fc epsilonRI by subpopulations of eosinophils, with a preferential expression of Fc epsilonRII/CD23 in the hypodense population. These results provide definitive evidence that the low-affinity IgE receptor (Fc epsilonRII) synthesized by human eosinophils is identical to the CD23 molecule expressed on B cells, and that the two CD23 isoforms a and b can be expressed by eosinophils.
