Isotypic analysis of specific antibody response in serum, saliva, gastric and rectal homogenates of Helicobacter pylori-infected patients.

The relationship between systemic and local humoral immune response to Helicobacter pylori is poorly understood. To further address this issue we measured, using ELISA, H. pylori-specific IgG and IgA antibodies in serum, saliva, gastric and rectal homogenates of H. pylori-infected patients. A total of 107 patients who underwent upper GI endoscopy and/or sigmoidoscopy were studied. The isotypic pattern of H. pylori-specific antibodies appeared to differ at the serum, salivary, gastric and rectal mucosa level. Serum H. pylori IgG titers were higher than those of the serum-specific IgA. On the contrary, in saliva samples H. pylori IgA titers were higher than specific IgG titers. In gastric homogenates, specific IgG and IgA titers were similar. H. pylori-specific IgG were detectable in rectal homogenates but no or very low H. pylori-specific IgA were found in the same material. Furthermore, no difference was found in H. pylori IgG and IgA in serum, saliva and gastric homogenates between duodenal ulcer and non-ulcer dyspepsia patients. Data of the present study indicate that, in H. pylori-infected patients, the specific immune response is as follows: (1) it involves the secretory immune system; (2) it is paralleled by the specific salivary IgA; (3) it does not differentiate duodenal ulcer from non-ulcer dyspepsia patients; and (4) it does not take place in the large bowel.