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Alpha-gal-specific human IgE promotes both alpha-gal-induced and antigen-independent allergic effector cell
Yinghui Wang1, Yugen Zhang2, Christa Dudley2
1Division of Rheumatology, Allergy, and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, NC; Thurston Arthritis Research Center, University of North Carolina at Chapel Hill, Chapel Hill, NC; Allergy Mast Cell Disorders Program, Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC; Division of Allergy and Immunology, Department of Pediatrics, Food Allergy Initiative, University of North Carolina at Chapel Hill, Chapel Hill, NC.
Background:
In alpha-gal syndrome (AGS), IgE antibodies form against the glycan galactose-α-1,3-galactose (alpha-gal) in mammal products rather than food proteins. Alpha-gal glycolipids and glycoproteins activate human basophils sensitized with AGS plasma in an IgE-dependent fashion. However, it is unknown whether alpha-gal specific IgE (sIgE), independent of other blood proteins, is sufficient for mediating basophil and mast cell activation.
Objective:
We sought to determine whether alpha-gal antigens could activate passively sensitized rat basophilic leukemia (RBL) SX-38 cells, which express human IgE receptors and are commonly used to model allergen/IgE-mediated mast cell activation in food protein allergy.
Methods:
Using the clustered regularly interspaced short palindromic repeats technology, we created a novel, alpha-gal-deficient RBL cell line, alpha-gal knockout RBL SX-38, passively sensitizing cells with sera from AGS donors or with novel alpha-gal sIgE clones, and then stimulated with alpha-gal glycoproteins. To assess effector cell activation, we measured cell surface expression of activation marker CD63 by flow cytometry and mediator release through β-hexosaminidase release assays.
Results:
After alpha-gal antigen stimulation, the percentage of CD63+ alpha-gal knockout RBL SX-38 cells sensitized with AGS sera increased 3-fold compared with cells sensitized with control serum. Select human AGS IgE clones facilitated alpha-gal antigen-dependent and antigen-independent CD63 upregulation. Cells sensitized with pooled AGS sera released β-hexosaminidase in an alpha-gal-independent fashion. We saw no β-hexosaminidase release above background in cells sensitized with alpha-gal sIgE clones.
Conclusions:
Certain alpha-gal-specific human IgE clones may partially activate allergic effector cells independent of antigen, potentially lowering thresholds for subsequent alpha-gal-induced or antigen-independent allergic effector cell degranulation. This may affect duration and severity of allergic symptoms in patients with AGS.
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