3 The humoral immune system in coeliac disease

IgA is transported into intestinal secretions to perform exclusion of luminal antigens. The prerequisites are antigen sampling by the Peyer's patch M cells, antigen processing by antigen-presenting cells, and presentation of antigenic peptides by HLA class II molecules to immunocompetent T cells. The basis for intestinal immunity is the maturation cycle of specifically primed T and B cells from the gut-associated lymphoid tissue via mesenteric lymph nodes and peripheral blood back to the intestinal lamina propria. In coeliac disease, patients are sensitized against gluten and serum gliadin antibodies are often detected. Gliadin antibodies are also found in other gastrointestinal diseases, other disorders and in healthy individuals not carrying the coeliac disease-specific DQA/DQB alleles. On the other hand, serum reticulin and endomysium autoantibodies are both sensitive and highly disease-specific. Positivity in patients with normal jejunal morphology indicates latency of coeliac disease. These tissue autoantibodies are directed against fibroblast-derived extracellular matrix proteins. The immune system is involved in the amplification and perpetuation of the abnormalities of the intestinal mucosa in coeliac disease. The role of antibody in the pathogenesis remains unknown. The author hypothesizes gluten-triggered autoimmune mechanism to be operative.