Cat allergy triggers uncovered
Scientists at the University of Cambridge have unlocked the triggers behind allergic reactions to cats, which could lead to new preventative treatments.
Until now, immune responses to cat allergens have been poorly understood, but scientists have now uncovered how the cat protein Fel d 1 triggers an inflammatory response in the immune system.
Fel d 1 is the most common cause of severe allergic reactions to cats, and is found in microscopic pieces of skin shed from animals - also known as dander.
Scientists found that when Fel d 1 is in the presence of the environmental bacterial toxin, lipopolysaccharide (LPS), it activates the pathogen recognition receptor, Toll-like receptor 4 (TRL4).
In order to determine how the protein causes allergic reactions, scientists exposed human cells to cat and dog dander proteins, when low levels of LPS were present, and when LPS was absent.
It was discovered that when LPS was present, signals to the immune system increased. In addition, researchers found that the part of the immune system that recognises the LPS-contaminated protein is TRL4, which also plays a part in allergic reactions to dust mite allergens and the metal nickel.
Lead author of the research, Dr Clare Bryant, explained: "How cat dander causes such a severe allergic reaction in some people has long been a mystery.
"Not only did we find out that LPS exacerbates the immune response’s reaction to cat dander, we identified the part of immune system that recognises it, the receptor TLR4."
Following this discovery, scientists used a drug which inhibits the TRL4 response, and found that as a result, the effect of dander protein on human cells was blocked, and the immune response prevented.
Other research has similarly found that the dog allergen, Can f 6, boosts signals to the immune system when LPS is present. Researchers therefore believe that TRL4-inhibiting drugs could also benefit those suffering from dog allergies.
Dr Bryant concluded: "As drugs have already been developed to inhibit the receptor TLR4, we are hopeful that our research will lead to new and improved treatments for cat and possibly dog allergy sufferers."
Veterinary practices are being urged to help owners safely dispose of any unused and expired pet medicines - not just antibiotics - during November's Animal Medicines Amnesty. 
