Development of a new method for the determination of immune responses in the human stomach.

The discovery of the gastric pathogen Helicobacter pylori has created a need for accurate methods to study immune responses locally in the human stomach. Therefore, we have developed a quick and easy method for extraction of antibodies from gastric biopsies using saponin and compared this method with the more laborious analysis of antibody-secreting cells (ASCs) from gastric biopsies. We have also analyzed the antibody content in gastric aspirates, saliva and plasma. There was a strong correlation between the total IgA levels in the biopsy extracts and the frequencies of IgA-secreting cells. In addition, the IgA and IgG levels against a H. pylori whole membrane preparation and purified urease in the biopsy extracts correlated well with the frequencies of specific IgA and IgG secreting cells. However, the antibody levels in gastric aspirates, saliva and plasma specimens did not correlate with the frequencies of corresponding ASC in the gastric biopsies. Thus, the saponin extraction method is suitable for monitoring local antibody responses in the stomach, while analyses of gastric aspirates, saliva or plasma are not appropriate for this purpose.