SYSTEMIC AND MUCOSAL HUMORAL RESPONSES TO HELICOBACTER-PYLORI IN GASTRIC-CANCER

The systemic IgG response to Helicobacter pylori was examined in 70 pa tients with gastric cancer. H pylori IgG antibodies were assayed by en zyme linked immunosorbent assay (ELISA), and serological recognition o f H pylori antigens was characterised by western blotting. A percentag e of 78.5 were seropositive by ELISA. Two of five patients under age 5 0 were seronegative. Positivity was unrelated to age, sex, tumour type , or site. Ninety one per cent of ELISA positive cancer patients recog nised the H pylori cytotoxin associated 120 kilodalton (kD) protein, s ignificantly more than a control group of 47 ELISA positive patients w ith non-ulcer dyspepsia (72%). Four of 15 ELISA negative cancer patien ts also showed recognition of this protein in western blots. Mucosal I gA responses to H pylori were examined by immunoblotting supernatants of in vitro cultured resected antral mucosa in an overlapping group of 19 gastric cancer patients. Eighteen had a positive response, includi ng 10 of 11 negative for H pylori by biopsy urease testing. The system ic and local immunoblotting results show that the high seroprevalence of H pylori antibodies detected by ELISA is nevertheless an underestim ate of past infection. Dyspepsia screening policies based solely on H pylori ELISA would miss some young patients with gastric cancer. Furth er study of the relation of the H pylori cytotoxin to gastric precance rous lesions is warranted.