RESUMO
The characterization of target antigens in several autoimmune disorders has made it possible to develop antigen-specific immunoassays that are superior in terms of sensitivity, specificity, reproducibility and ease of standardization, compared to immunohistological methods that are highly subjective, rely on skilled technicians and are not applicable to large-scale studies. In the case of celiac disease (CD), tissue transglutaminase (tTGase) has been identified as a major autoantigen, and antibodies against this molecule are present in most CD patients before gluten is removed from diet. In general, anti-tTGase detection assays detect the presence of IgA class antibodies, but these immunoglobulins are absent among patients with IgA deficiency, a frequent condition in which CD is very prevalent. In this report, we have analyzed 64 patients at diagnosis of CD for the presence of antibodies against tTGase of both IgA (TGA) and IgG (TGG) classes, using anti-IgA antibodies or Protein A, respectively, for the immunoprecipitation of 35S labeled, in vitro transcribed and translated human recombinant tTGase. In our hands, the TGG assay matches TGA in terms of sensitivity (97%) and specificity (100%), and besides, the combination of both assays is able to detect antibodies in all patient samples. The method described uses only 6 microl of serum, can be adapted to automated large-scale analysis and, in combination with other antigens, can be used for the simultaneous screening of other autoimmune diseases, like type 1 diabetes mellitus.