[IgA-antibodies against Helicobacter pylori in gastric secretions: gastric secretory immune response or salivary contamination?].

IgA anti-HP concentrations in both gastric juice and saliva samples of 40 HP+ patients (15 f, 25 m) randomly referred for upper GI-endoscopy were measured. The presence of HP was investigated using histology (H&E and Giemsa stain), rapid urease test (CLO) and serology (Cobas Core Anti-H. pylori EIA, F. Hoffmann-La Roche). IgA anti-HP in gastric juice and saliva was determined by ELISA; the same HP antigen was used as for serology (FPLC-purified native cell surface antigens including urease, free of cross-reacting flagellar proteins). The 40 HP+ patients were positive for HP by all three methods (except 4x CLO false neg, 1x serology false neg). A control group consisted of 12 patients (6 f, 6 m) with no HP detectable by each of the three methods used. No correlation was discernible between IgA anti-HP concentration in saliva and gastric juice of HP-positive patients (R = 0.05). In contrast, the correlation coefficient in HP-negative patients was R = 0.69 (p < 0.02). Great interindividual differences in specific IgA concentrations of both secretions were found. Surprisingly, in saliva and gastric juice IgA anti-HP was also detectable in some subjects negative for HP by all three tests applied. This finding remains to be elucidated but could represent ongoing local immune response in the absence of HP gastritis. In conclusion, saliva was found to contain IgA binding to HP-antigen. In HP-negative subjects contamination of gastric juice by saliva seems to be responsible when small concentrations of IgA anti-HP antibodies were detectable in gastric juice.(ABSTRACT TRUNCATED AT 250 WORDS)