They have identified a 'candidate gene' that is strongly implicated in passing on a predisposition to asthma in certain families who possess mutations in this region of their genetic material.
A team of researchers from Oxford University began the search for the genetic basis of allergies that underlie asthma and hay fever seven years ago. Three years later, the scientists localised the gene to a region of chromosome 11, one of the 23 pairs present in most human cells, but said it could be any one of up to 1,000 genes.
Now they have narrowed the search to 100 genes and their latest research has identified one of these genes as the most likely candidate responsible for conferring a predisposition to allergy.
Bill Cookson, who leads the Oxford group with Julian Hopkin, warned that the discovery had not been confirmed. 'If this candidate gene does not turn out to be the gene in question, it may take another four years to find it among the 100 genes we are searching among. If this is the gene, we are at least 10 years, or even 15 years from effective therapy.'
The Oxford team, which is funded by a medical charity, the Wellcome Trust, publishes its latest results in tommorrow's issue of the Lancet. The team has studied 400 people from 70 families with a history of asthma or hay fever.
Dr Cookson said that there were other causes of asthma other than allergies and this particular gene accounted for 'at most' 60 per cent of allergies.
'There are definitely other allergy genes out there to be found,' he said. The gene on chromosome 11 is active only when it is inherited from the mother's side, so that another gene or genes must account for allergies and asthma inherited from the father.
Research on mice helped to identify the candidate gene, which appears to be responsible for a protein molecule found on the membrane of cells involved in triggering allergic reactions.
The molecule binds only to one antibody found in the blood. It then triggers a flow of chemicals out of the cell, leading to runny noses, sneezing, redness and the symptoms of an allergic reaction.
Wellcome has given about pounds 1m to the group. 'If this does turn out to be the gene, we hope to instigate an even bigger research programme,' Dr Cookson said.