Shetland ponies midge study ‘could beat allergies’

Scientists found that when stung by midges, some Shetland ponies became immune. Picture: Ian Rutherford
Scientists found that when stung by midges, some Shetland ponies became immune. Picture: Ian Rutherford
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TINY Shetland ponies’ have played a starring role in study by Scots scientists who found their immune system might offer clues to understanding how ­people could be prevented from developing allergies.

Researchers at the University of Edinburgh who examined how 20 Shetland ponies reacted to midge bites have shown for the first time that the horse immune system can respond in a way that prevents, rather than triggers, allergic reactions.

We believe this finding could have direct practical implications

Dr Dietmar Zaiss

The ponies’ were used in the study because their immune response to midge bites is similar to what happens in people with allergies.

It was previously thought that ponies which do not suffer an allergic reaction to bites do so because their immune system does not recognise allergens carried by the insects, and as a result does not respond.

However, the study revealed that all horses respond and that their immune system can act in two different ways in response to the irritants in midge bites.

One of these responses produces allergy symptoms – such as itching and inflammation – while the other prevents an allergic reaction, researchers say.

The team found that after being exposed to midges, the horse immune system can release various types of factors – known as cytokines – which affect the behaviour of other cells.

Ponies that react to midge bites release cytokines – known as IL-4 – which trigger allergy symptoms.

In ponies not sensitive to bites, another cytokine – INF-g – is released, which blocks different immune cells that would otherwise trigger allergic reactions.

The team said that by priming the human immune system to respond to allergens in a way that does not trigger reactions, it could be possible to prevent people developing sensitivities.Allergies are caused by a complex interaction between genetic and environmental factors.

The reason some individuals develop sensitivities to certain substances, while others do not, is not fully understood. It is unclear what causes the immune system to activate a protective response over an allergic one.

Dr Dietmar Zaiss, of the university’s school of biological Sciences, who led the study, said: “To our knowledge, this is the very first study of a natural allergic disease in which we can show that immune responses to allergens can take two directions, either leading to allergy or to tolerance.

“We believe this finding could have direct practical implications, for example by helping immune responses to choose the “right” direction in individuals whom we would like to protect from developing occupation-associated allergies”.

The study, published in the journal Plos One, was funded by the Dutch Foundation for Technical Science and carried out in the Netherlands. Jane Dennis, one of the editors of the Shetland Pony Stud-Book Society Magazine, said: “I would be very interested to know if this will be aimed at producing a cure or immunisation.”