Gluten and celiac disease--an immunological perspective

Gluten, a complex protein group in wheat, rye, and barley, causes celiac disease (CD), an autoimmune enteropathy of the small intestine, in genetically susceptible individuals. CD affects about 1% of the general population and causes significant health problems. Adverse inflammatory reactions to gluten are mediated by inappropriate T-cell activation leading to severe damage of the gastrointestinal mucosa, causing atrophy of absorptive surface villi. Gluten peptides bind to the chemokine receptor, CXCR3, and induce release of zonulin, which mediates tight-junction disassembly and subsequent increase in intestinal permeability. Proinflammatory cytokine IL-15 also contributes to the pathology of CD, by driving the expansion of intra-epithelial lymphocytes that damage the epithelium and promote the onset of T-cell lymphomas. There is no cure or treatment for CD, except for avoiding dietary gluten. Current gluten thresholds for food labeling have been established based on the available analytical methods, which show variation in gluten detection and quantification. Also, the clinical heterogeneity of celiac patients poses difficulty in defining clinically acceptable gluten thresholds in gluten-free foods. Presently, there is no bioassay available to measure gluten-induced immunobiological responses. This review focuses on various aspects of CD, and the importance of gluten thresholds and reference material from an immunological perspective.