Immunoglobulin-E-bearing cells in skin biopsies of horses with insect bite hypersensitivity.
Authors: van der Haegen A, Griot-Wenk M, Welle M, Busato A, von Tscharner C, Zurbriggen A, Marti E
Journal: Equine veterinary journal
Summary
# Editorial Summary: IgE and Mast Cells in Equine Insect Bite Hypersensitivity Insect bite hypersensitivity (IBH) represents a common allergic dermatitis in horses, yet the precise immunological mechanisms driving the condition remain incompletely understood. Van der Haegen and colleagues employed immunohistochemistry and in situ hybridisation techniques on skin biopsies to determine whether immunoglobulin-E (IgE) and mast cells participate in IBH pathogenesis. Both acute and chronic IBH lesions demonstrated substantially elevated IgE-bearing cells in the dermis and epidermis (466 and 236 cells/mm² respectively) compared to healthy skin (110 cells/mm²), with acute lesions showing particularly elevated IgE messenger RNA expression (2.8 versus 0.0 cells/mm²); notably, mast cell populations were likewise significantly increased in acute IBH biopsies, identified via both metachromatic staining and tryptase-specific markers. These findings establish IgE-mediated reactions as central to IBH pathogenesis and suggest that targeting mast cell degranulation or IgE production may offer novel therapeutic avenues—a consideration of particular relevance given that current management remains largely based on environmental control and antihistamines rather than immunologically targeted interventions.
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Practical Takeaways
- •IBH is confirmed as an IgE-mediated allergic condition, suggesting that immunological management strategies targeting IgE or mast cell stability may be therapeutically relevant
- •The presence of elevated mast cells and IgE in IBH lesions supports consideration of antihistamines and mast cell stabilizers as treatment options
- •Skin biopsy findings can differentiate IBH from dermatomycosis based on IgE-mRNA and mast cell markers, aiding diagnostic accuracy in horses with pruritic dermatitis
Key Findings
- •IgE protein-bearing cells were significantly elevated in acute and chronic IBH lesions (466 and 236 cells/mm²) compared to healthy skin (110 cells/mm²)
- •IgE-mRNA positive cells in acute IBH dermis were 2.8 cells/mm² versus 0.0 in healthy skin, indicating active IgE production
- •Mast cell counts were significantly higher in acute IBH dermis using both metachromatic (160 vs 62 cells/mm²) and tryptase-specific staining (120 vs 69 cells/mm²)
- •Double labelling identified cells expressing both IgE protein and mast cell enzymes, supporting IgE-mediated immune involvement in IBH pathogenesis