Inadequate response to H2-receptor antagonists. Absence of parietal cell cAMP-stimulating autoantibodies.

In peptic ulcer patients with adequate (AR; N = 16) and inadequate response (IR; N = 20) to H2-receptor antagonists, the presence of parietal cell cAMP-stimulating autoantibodies was studied. Serum Ig fractions from these patients and 10 control subjects were examined to test whether they could stimulate cAMP production in a gastric cell line model. The human cell line HGT-1 was found to be a sensitive in vitro model for the cAMP stimulation assay as histamine (10 microM) increased by 11-fold the production of cAMP. Neither IgG (4 mg/ml) nor IgG-free Ig fractions (1 mg/ml) isolated from the blood of AR or IR affected cAMP production in the HGT-1 cells. The results obtained with the cAMP stimulation assay were confirmed by indirect immunofluorescence measurements based on frozen sections of rat stomach and kidney. No specific staining of rat parietal cells could be observed with patient sera. In addition, human gastric biopsies of the oxyntic mucosa from the same patients were studied for immunoreactive cell populations to assess organ-specific autoimmune processes. Biopsy specimens from AR and IR showed increased lymphocytic infiltrates, usually associated with gastritis. However, no significant differences in location of various cell populations between AR and IR could be observed. Our findings do not support a recent hypothesis that poor response to treatment with H2-receptor antagonists is due to the presence of autoantibodies.