A study led by Dr Scott Commins of the University of Virginia and presented at a recent meeting of the American Academy of Allergy, Asthma & Immunology suggest that the compound alpha-galactose which is produced in most mammals, and therefore found in meat, but not in humans, could be the cause of a number of hitherto unexplained anaphylactic reactions.
Commins and colleagues screened blood samples from 60 patients, testing for the antibody to alpha-galactose. The people in the study (22 at the University of Virginia, 20 at the University of Tennessee and 18 at John James Medical Center in Australia) had had anaphylaxis with no apparent cause.
Twenty-five tested positive for alpha-galactose and no other patterns were found that would have otherwise explained the cause of their anaphylaxis.
Usually anaphylaxis occurs within minutes of eating a food but in this case the reaction appears to be delayed for several hours.
While more details on this allergy will only come with additional research, Commins said the preliminary results suggest that people with certain blood types - specifically B and AB - may be less likely to have this type of allergy than those with other blood types. He also said the research shows that those who have been bitten by ticks or certain other blood-sucking insects may be more likely to have this allergy although the researchers feel that this may not having anything do with a specific infection, as in Lymes' disease.
Delayed anaphylaxis, angioedema, or urticaria after consumption of red meat in patients with IgE antibodies specific for galactose-alpha-1,3-galactose.
Commins SP, Satinover SM, Hosen J, Mozena J, Borish L, Lewis BD, Woodfolk JA, Platts-Mills TA. Asthma and Allergic Diseases Center, University of Virginia Health System, Charlottesville, VA, USA.
J Allergy Clin Immunol. 2009 Feb;123(2):426-33. Epub 2008 Dec 13.
Carbohydrate moieties are frequently encountered in food and can elicit IgE responses, the clinical significance of which has been unclear. Recent work, however, has shown that IgE antibodies to galactose-alpha-1,3-galactose (alpha-gal), a carbohydrate commonly expressed on nonprimate mammalian proteins, are capable of eliciting serious, even fatal, reactions.
We sought to determine whether IgE antibodies to alpha-gal are present in sera from patients who report anaphylaxis or urticaria after eating beef, pork, or lamb.
Detailed histories were taken from patients presenting to the University of Virginia Allergy Clinic. Skin prick tests (SPTs), intradermal skin tests, and serum IgE antibody analysis were performed for common indoor, outdoor, and food allergens.
Twenty-four patients with IgE antibodies to alpha-gal were identified. These patients described a similar history of anaphylaxis or urticaria 3 to 6 hours after the ingestion of meat and reported fewer or no episodes when following an avoidance diet. SPTs to mammalian meat produced wheals of usually less than 4 mm, whereas intradermal or fresh-food SPTs provided larger and more consistent wheal responses. CAP-RAST testing revealed specific IgE antibodies to beef, pork, lamb, cow's milk, cat, and dog but not turkey, chicken, or fish. Absorption experiments indicated that this pattern of sensitivity was explained by an IgE antibody specific for alpha-gal.
We report a novel and severe food allergy related to IgE antibodies to the carbohydrate epitope alpha-gal. These patients experience delayed symptoms of anaphylaxis, angioedema, or urticaria associated with eating beef, pork, or lamb.
First published in February 2009
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