Allergy to cats is common

The Imperial College London team topped up a key immune system component which controls allergic responses.

They told the Public Library of Science Medicine their approach may combat a range of allergies, and even autoimmune diseases, such as multiple sclerosis.

It comes two weeks after Californian scientists developed a fused protein technique to fight allergies to cats.

This discovery is a hugely important step in our understanding of how immunity and inflammation play a role in allergic reactions Dr Mark Larch�

In the UK, pets are the second most important cause of allergy in the home, and 50% of asthmatic children are allergic to cats.

Cat allergen is present on very small particles that readily become airborne when disturbed and are easily inhaled.

Lead researcher Dr Mark Larch�, said: "This discovery is a hugely important step in our understanding of how immunity and inflammation play a role in allergic reactions.

"Although we have known about the role of these regulatory immune cells for a number of years, this is the first time we have found a way to manipulate them to help control allergic reactions."

The component which the London team topped up in the body during tests was the CD4+ regulatory T-cells, which control responses to allergic triggers.

There are a number of types of T-cells in the body including T-helper 1, which are important in autoimmune diseases, T-helper 2, which are important in allergies, and T-regulatory cells.

In allergic diseases, the body produces too many T-helper 2 cells, and not enough T-regulatory cells.

This can result in asthma, hay fever and allergic eczema.

Injections

The researchers injected volunteers with protein fragments similar to those which trigger cat allergy.

Because the fragments lacked the 3D structure of the whole proteins, they did not trigger an allergic reaction themselves - but they did stimulate the immune system to begin producing more T-regulatory cells.

The researchers found that this helped to minimise subsequent allergic reactions.

So far they have carried out studies in small groups of volunteers, but are looking to organise a much larger clinical trial this summer.

Dr Larch� told the BBC News website that it was possible a vaccine could be avaiable in four or five years.

He said: "At the moment we are using the injection route, but it may end up being a tablet that dissolves under the tongue."

Autoimmune diseases

The researchers believe same approach might also help to combat autoimmune diseases, such as type 1 diabetes and multiple sclerosis.

These diseases arise when too many T-helper 1 cells are produced, and start to attack the body's own tissue.

Using a similar approach to boost T-regulatory cell numbers may help to dampen down this attack.

Philippa Major, of the charity Asthma UK, said: "Getting outcomes from research is a slow process and this important development plays a key part in understanding the role of the way the immune system can be targeted."