Disparity between mucosal and serum IgA and IgG in Helicobacter pylori infection

Mucosal IgA and IgG are involved in the immune defense against Helicobacter pylori in infected patients. In contrast to IgG, IgA is transported into the gastric lumen and is responsible for the first-line defense. Therefore antigens recognized by mucosal IgA are possible candidates for vaccination. This study compared the IgA and IgG immune response to H. pylori in the gastric mucosa and that in the serum of 21 patients with H. pylori gastritis by the immunoblotting technique. In particular, mucosal IgA immune response against the urease antigen of H. pylori was studied in detail, as vaccination with this antigen was not curative in men. The results show that mucosal IgA was not represented by serum IgA and IgG, and that the H. pylori specific mucosal IgA and IgG immune responses differ in antigen-recognition pattern. This disparity may reflect the different transport ways and functions of these two immunoglobulin isotypes. Furthermore, mucosal IgA specific for urease was found inconsistently in patients with H. pylori gastritis. As vaccination antigens should induce an appropriate mucosal IgA immune response against H. pylori, our findings may have important implications for the selection of antigens for vaccination against H. pylori.