Phenotype and function of IgE-binding monocytes in equine Culicoides hypersensitivity

Area of Science:

• Veterinary Immunology
• Equine Allergy Research
• Monocyte Phenotyping

Background:

• Human IgE-binding monocytes are implicated in allergic diseases, but their role remains unclear.
• Understanding these cells in horses could reveal mechanisms of IgE-mediated conditions.

Purpose of the Study:

• Characterize IgE-binding monocytes in equine peripheral blood.
• Investigate the phenotype and frequency of these cells in allergic and non-allergic horses exposed to Culicoides midges.
• Determine the cytokine production profile of equine IgE-binding monocytes.

Main Methods:

• Flow cytometry to identify IgE-binding monocytes (IgE+/MHCIIhigh/CD14low) using an FcεRI αɣ variant.
• Monthly analysis of monocytes in Culicoides-exposed allergic and non-allergic horses.
• Measurement of CD16 expression, serum total IgE, and monocyte surface IgE densities.
• Assessment of cytokine production (IL-10, IL-4, IL-17A, IFN-γ) following IgE crosslinking.

Main Results:

• Equine IgE-binding monocytes were identified as IgE+/MHCIIhigh/CD14low cells.
• Monocyte phenotype and frequency were consistent across horses, regardless of allergic status or Culicoides exposure.
• All horses upregulated CD16 expression on IgE-binding monocytes after initial Culicoides exposure.
• A positive correlation was observed between serum total IgE and monocyte surface IgE densities.
• Equine IgE-binding monocytes produced IL-10 but not IL-4, IL-17A, or IFN-γ upon IgE crosslinking.

Conclusions:

• Equine IgE-binding monocytes have been characterized for the first time.
• These cells consistently produce IL-10, suggesting a regulatory role in IgE-mediated immune responses.
• Further research into these monocytes may elucidate connections between regulation and cellular mechanisms in equine allergic diseases.