Interaction between Helicobacter pylori and human gastric mucosa revisited by electron microscopy: still something...

Helicobacter pylori (Hp) is a pathogen which causes gastric diseases from gastritis to ulcer, cancer, and MALT Lymphoma. The higher grade of virulence belongs to strains harbouring CagA oncoprotein. Hp cag Pathogenicity Island encoded Type IV Secretion System (T4SS) is supposed to form needle-like structures (pili) on Hp surface that injects cagA into the host cell cytoplasm at basolateral membrane level. Other structures such as membranous appendages have also been described on Hp surface membrane. These data were obtained from cultured cells. The aim of the present, preliminary, retrospective, study was to investigate the morphological expression of T4SS also in human gastric biopsies and revisit the morphological aspects of bacteria and host interaction.

We reviewed our previous morphological findings on over 300 scanning electron micrographs of 109 gastric bioptic specimens.

1) Needle-like structures (Pili) and membranous appendages have been found at the Hp gastric cell surface interface; 2) Hp polar flagella merge to apical mucous cell membrane; 3) some gastric cell microvilli became taller and projected towards bacteria; 4) in lining epithelium basal membrane holes in which bacteria penetrate are clearly visible.

Hp T4SS associated structures have also been observed in human biopsies. Pili could also take nutrients from gastric mucous cells (iron); the polar flagella could anchor Hp tightly to mucous cells; the tall microvilli projected to Hp could represent defence or affinity.