Tick bites: A common cause of IgE antibodies to alpha-gal
Two novel forms of anaphylaxis have been defined recently: i) acute reactions during the first infusion of cetuximab and ii) delayed anaphylaxis to red meat. In each case, these reactions were shown to be occurring in patients who had IgE antibodies to the oligosaccharide galactose alpha-1,3-galactose, which is a mammalian blood group substance.
In a study published in the April 2011 issue of The Journal of Allergy and Clinical Immunology (JACI), Commins et al have now reported evidence that tick bites predominantly from the Lone Star Tick cause these IgE antibodies. The evidence includes prospective data on three subjects, a strong association with a history of tick bites, a good correlation (r = 0.67, p <0.001) between IgE antibodies to tick extract and IgE antibodies to alpha-gal, and finally extensive epidemiological evidence that these IgE antibodies are only found in areas where tick bites are common. These IgE antibodies are common (i.e., 15-20% of adults) in an area that includes TN, NC, AR, MO, and VA.
The results are important clinically because the cases of anaphylaxis starting 3-6 hours after eating beef or pork can be very confusing. The history usually includes prolonged pruritic reactions to ticks. The diagnosis becomes probable with positive skin tests to mammalian extracts and can be confirmed by a blood test for IgE to alpha-gal.
The Journal of Allergy and Clinical Immunology (JACI) is the official scientific journal of the AAAAI, and is the most-cited journal in the field of allergy and clinical immunology.