CD40LG and Helicobacter pylori infectious disease: The observed high seroprevalence of H. pylori infection in our study could be explained due to the following key facts: 1) It is clearly known that during H. pylori infection IgM is the first and early antibody to be produced [30], and later IgG develops [31], which remain with high titer and detectable indefinitely even after eradication of H. pylori.