Induction of various cytokines and development of severe mucosal inflammation by cagA gene positive Helicobacter pylori strains

Abstract

Background —Helicobacter pylori strains possessing the cagA gene are thought to induce interleukin 8 (IL-8) in gastric mucosa. However, it is still unclear whether a relation exists between the cagA gene and the expression patterns of cytokines other than IL-8. Aims — To investigate the relation between the cagA gene and the production of various cytokine proteins using an enzyme linked immunosorbent assay (ELISA). Patients and methods — In 184 patients, the cagA gene was detected by polymerase chain reaction (PCR), and levels of production of IL-1β, IL-6, IL-7, IL-8, IL-10, and tumour necrosis factor α (TNF-α) in antral biopsy specimens were measured by ELISA. Results— Mucosal levels of IL-1β, IL-6, IL-8, and TNF-α were significantly higher in H pylori positive than in H pylori negative patients. Furthermore, the mucosal levels of IL-1β and IL-8 were significantly higher in specimens infected with cagA positive strains than in those infected with cagA negative strains. In H pylori positive patients, the mucosal level of IL-8 was closely correlated with that of IL-1β (p<0.0001), and the mucosal level of IL-6 was closely correlated with that of TNF-α (p<0.0001). Conclusion— These findings suggest that the ability to induce cytokines differs among the strains; cagA + strains induce various kinds of cytokines and may cause severe inflammation, whereas cagA − strains induce IL-8 and IL-1β only weakly and may cause only mild inflammation. However, as most patients infected with the cagA + strains have gastritis, these strains may not be equivalent to ulcerogenic strains.