Peripheral blood basophils are the main source for early interleukin-4 secretion upon in vitro stimulation with Culicoides allergen in allergic horses.
Authors: Raza Fahad, Babasyan Susanna, Larson Elisabeth M, Freer Heather S, Schnabel Christiane L, Wagner Bettina
Journal: PloS one
Summary
Culicoides hypersensitivity (CH) in horses involves a complex IgE-mediated allergic cascade, but the precise cellular mechanisms driving the initial Th2 immune shift remain incompletely understood. Researchers stimulated peripheral blood mononuclear cells from eight allergic and eight healthy horses with Culicoides allergen extract, measuring interleukin-4 (IL-4) production both during peak allergen exposure and during off-season months. Basophils—not T cells—emerged as the predominant IL-4 source in allergic horses following allergen stimulation, and notably, allergic horses maintained elevated basophil percentages year-round compared to controls. These findings suggest that basophil-derived IL-4 may represent a critical early innate signal that skews immune responses towards Th2 phenotype and perpetuates IgE production in CH-affected individuals. For practitioners managing equine allergic dermatitis, this work implies that modulating basophil activation or IL-4 signalling could offer novel therapeutic targets beyond conventional allergen avoidance and symptomatic treatment strategies.
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Practical Takeaways
- •Basophil-derived IL-4 appears to be a key driver of the allergic cascade in Culicoides hypersensitivity, potentially offering new therapeutic targets beyond simple allergen avoidance
- •The persistent elevation of basophil populations in allergic horses year-round suggests the immune dysregulation in these horses is chronic, not just seasonal, which may inform management strategies
- •Understanding that basophils—not T cells—provide the early immune signal could lead to development of basophil-targeted treatments that interrupt allergic responses before full Th2 commitment occurs
Key Findings
- •Peripheral blood basophils are the primary source of early IL-4 secretion in allergic horses upon Culicoides allergen stimulation, not T cells
- •Allergic horses maintained elevated basophil percentages year-round compared to healthy horses, even during non-exposure periods
- •IL-4 production from PBMC was similar between healthy and allergic horses during active Culicoides exposure, but higher in allergic horses during off-season months
- •IgE crosslinking triggered basophil IL-4 production in both healthy and allergic horses, suggesting basophils are primed to respond to allergen activation