Modulation of allergy incidence in icelandic horses is associated with a change in IL-4-producing T cells.

The research studied a type of allergic reaction in horses known as Equine Insect Bite Hypersensitivity (IBH), which was found to be influenced by T cell changes, particularly in relation to a cytokine known as IL-4.

Study Background

• The study was triggered by the observation that Icelandic horses born and raised in Iceland did not exhibit IBH, an allergic reaction caused by reactions to insect bites.
• However, upon migrating to mainland Europe, a high percentage of the horses developed the condition.
• Interestingly, the offspring of these transplanted Icelandic horses that are born in mainland Europe have a lower likelihood of contracting IBH.

Methodology

• The scientists examined the T helper cells (Th1 and Th2) and their related cytokines within these horses, both those originating from Iceland and those born in mainland Europe.
• Cytokines are proteins that play key roles in regulating immune responses.
• The study focused particularly on four cytokines – IFN-gamma, IL-4, IL-5 and IL-13 – and their mRNA counterparts.
• The horses’ Peripheral blood mononuclear cells (PBMC) were isolated and subjected to different stimulations involving T cell stimuli, IBH allergens, and unrelated allergens.
• The reactions of these cells in summer and winter were analyzed via flow cytometry and mRNA analysis.

Results and Findings

• The research found that horses presenting with IBH (regardless of their place of birth) showed a decrease in IFN-gamma mRNA and IFN-gamma-producing cells in the summer months.
• This was not observed in the winter months, indicating a seasonal effect on the immune response.
• Simultaneously, an increase in IL-4 mRNA levels and IL-4-producing cells were observed when horses were either born in Iceland or exhibiting IBH symptoms.
• However, there were no noticeable changes in IL-5 and IL-13 mRNA irrespective of the disease status or origin of the horses.
• The researchers also found that in healthy horses born in mainland Europe, IL-4 production was seemingly inhibited, possibly by the action of another cytokine known as IL-10.
• High IL-10 levels were found in the blood cells of healthy horses born in mainland Europe, potential evidence of IL-10’s role in countering IBH.

Conclusion

• The study concluded that the incidence of IBH in horses might be regulated by alterations in Th1/Th2 ratios, with the cytokine IL-10 possibly playing a major role.
• This provides new insights into the pathogenesis of equine IBH and indicates potential directions for future research, such as studying the role of IL-10 in preventing allergic reactions.