α-ガラ特異的ヒトIgEは、α-ガラ誘発性および抗原非依存性の両方のレルギーエフェクター細胞活性化を促進する
Yinghui Wang1, Yugen Zhang2, Christa Dudley2
1Division of Rheumatology, Allergy, and Immunology and Thurston Arthritis Research Center; Allergy Mast Cell Disorders Program, Department of Medicine; Department of Pediatrics, Food Allergy Initiative, Division of Allergy and Immunology.
Background:
In alpha-gal syndrome (AGS), immunoglobulin (Ig)E antibodies form against the glycan galactose-alpha-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, independent of other blood proteins, is sufficient for mediating basophil and mast cell activation.
Objective:
We determined whether alpha-gal antigens could activate passively-sensitized rat basophil 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 CRISPR, we created a novel, alpha-gal-deficient RBL cell line, AGKO RBL SX-38, passively sensitizing cells with sera from AGS donors or with novel alpha-gal-specific IgE clones, then stimulating 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, percentages of CD63+ AGKO RBL SX-38 cells sensitized with AGS sera increased 3-fold compared to 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-specific IgE clones.
Conclusion:
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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