Immunoglobulin E-bearing cells and mast cells in skin biopsies of horses with urticaria.

The research focuses on understanding the cause of urticaria (hives) in horses by examining presence of specific cell types and immunoglobulins in skin biopsies of afflicted horses compared to healthy controls and horses with other skin conditions.

Research Methodology

• The research investigators used skin biopsies from 32 horses which had a history of urticaria.
• These biopsies were stained using the toluidine blue staining method and a double-labelling method for substances known as chymase and tryptase.
• The researchers also employed immunohistochemistry, a technique to identify specific proteins in cells of a tissue section, to detect the presence of immunoglobulin E, or IgE.
• The results from these horses were compared with biopsies from horses suffering from different conditions – pemphigus foliaceus and insect bite hypersensitivity – and control horses which had healthy skin.
• The selection of staining and visualization methods ensured that factors such as formalin fixation time or biopsy site did not impact the results of the study.

Research Findings

• The research found no evidence of chymase-positive cells in any of the skin biopsies.
• All groups – those with urticaria, healthy controls, and those with other skin conditions – had cells that stained positively for tryptase and IgE in the epidermis and hair follicle papilla.
• There was a significant presence of these positively staining cells in the subepidermal dermis, a layer of skin, than in the deep dermis.
• Horses with urticaria were found to have significantly higher number of cells bearing IgE in the subepidermal dermis compared to control horses.
• A surprising finding was that horses with urticaria had significantly fewer mast cells in the subepidermal and deep dermis when stained with toluidine blue, especially in comparison with the horses suffering from insect bite hypersensitivity and pemphigus foliaceus.

Conclusions

• From the results and observations above, the study suggests that immune reactions involving IgE may play a significant role in causing urticaria in horses.
• While the presence of IgE and associated immune reactions were noticed in all horse groups, it was significantly more in the urticaria-afflicted horses, highlighting a potential role in the pathogenesis of the condition.