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Updated: May 5, 2026
Basophil Activation Test for Investigation of IgE-Mediated Mechanisms in Drug Hypersensitivity
Published on: September 16, 2011
Expression and modulation of FcepsilonRIalpha and FcepsilonRIbeta in human blood basophils
S S Saini1, J J Richardson, C Wofsy
1Department of Medicine, Division of Clinical Immunology, Johns Hopkins University School of Medicine, Baltimore 21224, USA.
Insights
Basophils exhibit variable IgE receptor (FcepsilonRIalpha:beta) stoichiometry, which impacts cellular responsiveness and can be modulated by IL-3. This variability is linked to FcepsilonRIalpha surface expression levels.
Area of Science:
- Immunology
- Cellular Biology
Background:
- The high-affinity IgE receptor (FcepsilonRI) is crucial for allergic responses.
- FcepsilonRI can assemble as a tetramer (alphabetaγ2) or trimer (αγ2), with FcepsilonRIbeta amplifying signaling.
- Regulation of FcepsilonRIalpha:beta stoichiometry is key to cellular responsiveness.
Purpose of the Study:
- To investigate variations in FcepsilonRIalpha and FcepsilonRIbeta protein expression in human basophils.
- To determine the relationship between FcepsilonRIalpha and FcepsilonRIbeta expression levels.
- To assess the impact of IL-3 on basophil FcepsilonRI expression and stoichiometry.
Main Methods:
- Western blotting to detect FcepsilonRIalpha and FcepsilonRIbeta protein.
- Flow cytometry to quantify surface FcepsilonRIalpha expression.
- Real-time PCR to measure FcepsilonRIbeta mRNA levels.
- Allergen-induced histamine release assay for functional response.
Main Results:
- Two FcepsilonRIalpha protein bands (50-kd and 60-kd) were identified; the 60-kd band correlated with surface expression.
- Surface FcepsilonRIalpha strongly correlated with FcepsilonRIbeta protein levels (Spearman R = 0.92, P <.01).
- The ratio of FcepsilonRIbeta to FcepsilonRIalpha varied 10-fold among donors and was linked to surface FcepsilonRIalpha; IL-3 increased beta subunit but not alpha.
Conclusions:
- Basophils display variable FcepsilonRIalpha:beta stoichiometry in whole cells.
- This stoichiometry can be modulated by IL-3 culture.
- Variable FcepsilonRI stoichiometry is related to FcepsilonRIalpha surface expression, influencing cellular signaling.
Background:
The IgE receptor (FcepsilonRI) may exist as a tetramer (alphabetagamma2) or a trimer (alphagamma2) because FcepsilonRIbeta is dispensable for membrane expression of FcepsilonRIalpha. FcepsilonRIbeta amplifies signaling of FcepsilonRI so that regulation of FcepsilonRIalpha:beta stoichiometry would affect cellular responsiveness.
Objective:
We examined basophils from a variety of donors for differences in their expression of FcepsilonRIalpha and FcepsilonRIbeta protein.
Methods:
Enriched blood basophils were assessed at baseline and after IL-3 culture for FcepsilonRIalpha and FcepsilonRIbeta protein by Western blotting, surface FcepsilonRIalpha by flow cytometry, and FcepsilonRIbeta mRNA by real-time PCR. Basophil functional response was measured by allergen-triggered histamine release.
Results:
For the FcepsilonRIalpha subunit, 2 protein bands with molecular weights of 50 kd and 60 kd were identified by Western blots. The 60-kd band correlated to surface-expressed FcepsilonRIalpha detected by flow cytometry (Spearman R = 0.78, P <.01). Surface FcepsilonRIalpha also correlated with FcepsilonRIbeta protein (Spearman R = 0.92, P <.01). FcepsilonRIbeta protein levels increased disproportionately with higher surface FcepsilonRIalpha expression. The ratio of FcepsilonRIbeta to FcepsilonRIalpha varied 10-fold among donors and correlated with surface FcepsilonRIalpha. Basophil 50-kd alpha protein levels were similar despite a 10-fold range in surface FcepsilonRIalpha expression, implying stores of this protein such as those found in eosinophils. Unlike eosinophils, the basophil 50-kd protein was lost with culture and was absent from supernatants. Levels of beta protein and mRNA were enhanced by IL-3 culture, whereas FcepsilonRIalpha expression (by flow cytometry and 60 kd) was not.
Conclusion:
These findings demonstrate variable stoichiometry of FcepsilonRIalpha:beta in whole cells and that this stoichiometry can be altered by IL-3 culture. With the assumption that all detected beta protein is surface expressed, these findings suggest a variable stoichiometry for FcepsilonRIalpha:beta that is also related to FcepsilonRIalpha surface expression.
