Expression of inducible nitric oxide synthase in epithelial cells, mucosa-associated lymphoid tissue, and regional lymph nodes of the stomach with Helicobacter pylori-associated peptic ulcer

This study examined expression of inducible nitric oxide synthase (iNOS) by means of antigen-retrieval immunohistochemistry of anti-iNOS antibody in 4 cases of the stomach with Helicobacter pylori (HP)-associated peptic ulcer and in 29 cases of non-neoplastic and neoplastic lymphatic tissue in order to understand pathogenicity of iNOS in HP-associated diseases. 1)Crypt foveolar epithelial cells in the stomach and covering squamous cells in the tonsil expressed iNOS， suggesting that iNOS is expressed as a part of mucosal defence mechanism. 2) Some germinal centers (GCs) in mucosa-associated lymphoid tissue (MALT) and in regional lymph nodes of the stomach expressed iNOS, suggesting that iNOS is expressed in the GCs as a part of immunity against HP infestation, although some GCs expressed iNOS in non-specific lymphadenitis. 3) Including foreign body type multinuclear giant cells in tuberculous lymphadenitis and foamy cells in the mesenteric lymph node, histiocytes expressed iNOS that would be induced in a part of foreign body reaction against bacteria. 4) Thymic epithelial cells expressed iNOS that may concern with apoptosis of thymocytes. 5)A few metastatic mammary carcinoma cells in a lymph node expressed iNOS that may have relation to metastatic activity. 6) GCs in atypical lymph follicles of the early marginal zone B-cell lymphoma in the skin expressed iNOS, suggesting a role of iNOS in lymphomagenesis. Consequently, iNOS, which is expressed in GCs of the lymphatic tissue of the stomach with HP infestation, would produce nitric oxide (NO) that effects on the immunity against HP and prepares microenvironment for MALT type/marginal zone B-cell lymphomagenesis