Immunopathogenesis of Food Allergy and Eosinophilic Gastrointestinal Disorders

Background: \- Food allergies are characterized by abnormal immune system responses to certain foods, such as peanuts, strawberries, and shellfish. Some individuals with these allergies have immediate allergic reactions on contact with the food in question and need immediate treatment to prevent severe complications. In contrast, eosinophil-associated gastrointestinal disorders are related disorders in which white blood cells in the intestinal tract react to certain foods, causing abdominal pain, nausea, and other digestion problems. Researchers are interested in studying these conditions to better understand how the immune system responds to food allergies. Objectives: * To examine how the immune system responds to food allergens. * To examine how certain white blood cells contribute to disease in individuals with food allergies and other inflammatory diseases. Eligibility: * Individuals between 18 and 65 years of age who have a history of (a) severe allergic reaction to peanuts (and have peanut-specific antibodies), (b) allergy or inflammatory disease, or (c) eosinophil-associated gastrointestinal disorder (with at least two documented food allergies). * Healthy volunteers between 18 and 65 years of age who have no known allergies or asthma. Design: * All participants will have a screening visit and a procedure visit. The procedure visit will take place within 30 to 60 days of the screening visit, and will take 3 to 4 hours depending on the procedure(s) done. * Participants will be screened with a physical examination and medical history, and will provide blood samples for testing. Participants with peanut or other allergies will have additional tests to determine their levels of sensitivity to certain foods. Participants with eosinophil-associated gastrointestinal disorder will provide stool samples for testing. * At the procedure visit, participants with peanut allergies and participants with other allergies will provide blood samples and have leukapherisis to collect white blood cells for examination. * At the procedure visit, healthy volunteers and participants with eosinophil-associated gastrointestinal disorder will provide blood samples and have leukapherisis to collect white blood cells for examination. In addition, some but not all of these participants will have a procedure called esophagogastroduodenoscopy (EGD), which will examine the esophagus, stomach, and small intestine. Participants who are scheduled to have EGD will be asked to fast for 6 hours before the procedure.

Food allergy refers to a number of disorders characterized by clinical diseases associated with abnormal immune responses to food antigens. Classical IgE mediated anaphylactic food allergy is characterized by immediate hypersensitivity, and has a prevalence of approximately 6% and 3% in children and adults, respectively. In contrast, eosinophil associated gastrointestinal disorders (EGIDs), including eosinophilic esophagitis (EoE) and eosinophilic gastroenteritis (EG), are food allergy associated disorders characterized by eosinophilic inflammation of the gut, typically without anaphylaxis. Progress in the treatment and management of these food allergies requires further understanding of the immunological pathogenesis of these disorders. A subset of peripheral blood food allergen specific interleukin (IL) -5 producing T cells that are present in EGID but not peanut allergic subjects has recently been characterized. The primary objective of this study is to determine if similar IL-5 producing T cells are present in the gut of EGID subjects. To this end, both EGID and healthy non-allergic subjects will be enrolled and gastrointestinal biopsies will be obtained for intracellular cytokine staining, RT-PCR and ELISA. Additionally, this protocol will supply blood and leukapheresis samples for exploratory studies on immunologic mechanisms underlying anaphylactic food allergy and EGIDs. A total of up to 400 subjects recruited from outside physician referrals and support groups, as well as from those in existing National Institutes of Health (NIH) protocols will be enrolled in this Clinical Center study.