Following endoscopy and participation in IRB Protocol #1698, for the symptomatic patients who are not taking any proton pump inhibitor, an H2 blocker, Ranitidine (ZantacÒ) 150 mg twice daily, will be started while the biopsy is being analyzed for histology and immunocytochemical stainings. This is usually completed within 2 weeks. Patients who showed positive reactivity in at least one biopsy sample taken during participation in Protocol #1698 with mAb Das-1 will be included in this study. Patients who have been taking a proton pump inhibitor (PPI) for longer than 3 months preceeding study entry are not eligible to participate in this study. Patients who have been taking proton pump inhibitors for 3 months or less at the time of the endoscopy and biopsy screening for mAb Das-1, may participate in this study 4 weeks after discontinuing the PPI (i.e., a 4 week washout period).