We performed immunohistochemistry experiments using synthetic antibodies on the gastrointestinal tract and kidney from acute Kawasaki disease patients. Significant gastrointestinal tract inflammation was present in only 2/7 patients, who had antigen detected at the site of inflammation. Antigen was not detected in kidney from 6 patients. The presence of antigen may be related to gastrointestinal pathology in acute Kawasaki disease.