Anaphylaxis to the carbohydrate side chain alpha-gal.

In 2007, the monoclonal antibody cetuximab caused severe hypersensitivity reactions during the first infusion in a region of the southeastern United States. Investigation of pretreatment sera established that they contained immunoglobulin (Ig) E against the oligosaccharide galactose-alpha-1,3-galactose (alpha-gal), which is present on the Fab of cetuximab. Alpha-gal is a blood group substance of nonprimate mammals. These IgE antibodies are also associated with delayed anaphylaxis to red meat (ie, to meat or organs of animals that carry this oligosaccharide). Evidence shows that the primary cause of these IgE antibodies is bites from the tick Amblyomma americanum or its larvae.