Comparison of serum and gut antibodies against two major antigens in celiac disease patients, the autoantigen transglutaminase 2 (TG2) and a deamidated gluten peptide (DGP) from food. The antigen-specific antibodies were affinity-purified from isolated total IgA of serum or gut biopsy secretions or from whole serum samples. Individual clonotypes could be identified among the purified antibodies based on matching to a database of IgH sequences obtained from antigen-specific gut plasma cells of the same patients.