Allergies - first born at increased risk

(Image credit www.about.com) 

A University of Carolina study monitoring 1200 newborns from the ‘Isle of Wight cohort’ found that first borns were more likely to carry a gene variant which raised their risk of developing an allergy before the age of 10.  The study suggested that a first born experienced different conditions in the uterus from subsequent siblings.

The researchers measured levels of an antibody called Immunoglobulin E (IgE) in the babies’ umbilical cord blood.  This is known to play a key role in the development of allergic responses.   First born babies were more likely to have high levels of IgE, and those that did were also more likely to show signs of an allergic response when they were subsequently tested, using a skin prick test, at the age of four and ten.

The researchers also believe they may have pinned down the genetics behind the difference to variations in a gene called IL13, which controls production of a stress hormone called a cytokine, which in turn influences levels of IgE. They found that first born children were more likely to carry a variant of IL13 which raises levels of the cytokine, and in turn IgE.

The researchers believe that birth order may affect expression of the gene during the foetal differentiation and development.

Lead researcher Dr Wilfried Karmaus said:

“We were not surprised that birth order had an effect on the development of the immune system, but were surprised that this interaction persisted at least through age ten … Our findings add to the evidence that allergic reactions are programmed during pregnancy and then effect the disease in later life. … This finding may partially account for the increasing prevalence of asthma and allergies in children in the last 30 years, primarily seen in the western world, as developed nations’ birthrates continue to decline.”

He said that if a way to modify those conditions could be found to make them more like those experienced by later born children, then potentially it might be possible to prevent 20-30% of all cases of asthma and allergy.

http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=2366045

Elaine Warburton  www.geneticsandhealth.com