Separate Gut Plasma Cell Populations Produce Auto-Antibodies against Transglutaminase 2 and Transglutaminase 3 in Dermatitis Herpetiformis

Dermatitis herpetiformis (DH) is an inflammatory skin disorder often considered as an extra intestinal manifestation of celiac disease (CeD). Hallmarks of CeD and DH are auto-antibodies to transglutaminase 2 (TG2) and transglutaminase 3 (TG3), respectively. DH patients have auto-antibodies reactive with both transglutaminase enzymes. Here it is reported that in DH both gut plasma cells and serum auto-antibodies are specific for either TG2 or TG3 with no TG2–TG3 cross reactivity. By generating monoclonal antibodies from TG3-specific duodenal plasma cells of DH patients, three conformational epitope groups are defined. Both TG2-specific and TG3-specific gut plasma cells have few immunoglobulin (Ig) mutations, and the two transglutaminase-reactive populations show distinct selection of certain heavy and light chain V-genes. Mass spectrometry analysis of TG3-specific serum IgA corroborates preferential usage of IGHV2-5 in combination with IGKV4-1. Collectively, these results demonstrate parallel induction of anti-TG2 and anti-TG3 auto-antibody responses involving separate B-cell populations in DH patients.