The clinical relevance of IgG food allergy testing through ELISA - Enzyme-Linked Immunosorbent Assay

Townsend Letter for Doctors and Patients, Jan, 2004 by Raymond M. Suen, Shalima Gordon

Other factors influencing the predominant immune response to food antigen include; genetic background and indigenous gut flora. With regards to the former, celiac disease for example, is believed to be due in part to aberrant antigen presentation. Over 95% of patients with celiac disease carry a DQ2 (HLA-DQ2) gene that encodes MHC II markers that present gliadin to T cells in the lamina propria. (44), (45) Cytokine release increases the expression of HLA-II, thus amplifying the immune response with resulting cell damage. These inflammatory mediators also increase gut permeability and promote the differentiation of B cells into IgG-antigliadin antibody-producing plasma cells. (46)

Indigenous gut microflora has been strongly implicated in competent induction of oral tolerance. The gastrointestinal tract contains about 100,000 billion, or three and one- half pounds worth of viable microflora of which there is a variation in number and type in the different regions of the intestine. (47) Lactobaccilli predominate in the small intestine, particularly in the middle and distal ileum, whereas Bifidobacteria increase in prevalence from the cecum to large intestine. Gut microflora are compulsory to the development of mucosal immuno-responsiveness--humoral and cell-mediated immunity, during the neonatal period, and serves to prime the GALT throughout the life of the individual. (48) Following birth, in the absence or delay of colonizing microflora, oral tolerance may be abrogated. Specifically, there is incomplete maturation and development of Peyer's patches, intraepithelial and lamina propria lymphocytes, in addition to decreased levels of plasma cells and IgA antibody production. (49) Clearly, defective development of the mucosal immune system in this way will incite deregulated inflammation and negatively influence the immune response to dietary antigens.

The mucosal surface represents the interface between the internal and external environments of the body that is in continual contact with a myriad of food proteins, invasive pathogens and indigenous flora on a daily basis. Discernment between infectious and noninfectious agents is therefore key to survival of the individual in his environment. Under normal circumstances down-regulation of the immune response governs oral tolerance to dietary antigens and indigenous flora of the gastrointestinal tract. (50), (51) The precise mechanisms involved in inducing oral tolerance to dietary antigens are imperfectly known. It is important to keep in mind that oral tolerance is a complex immune response that involves a precarious balance among several immune-mediated parameters. A glimpse into the competency of tolerance through IgG food allergy testing via the ELISA method is a simple tool for the practitioner to visualize the immunological response to dietary challenge in the patient. In practice, this assessment may guide treatment to nullify undue mediators of inflammation in the body that may be perpetuating a disease process.