title: Role of Helicobacter pylori infection in autoimmune diseases.
abstract: OBJECTIVE
  The etiology of most autoimmune diseases remains elusive. Prevailing evidence suggests an environmental trigger in a genetically susceptible individual. Helicobacter pylori (H. pylori) have managed to survive in a hostile environment in their host for long period and have evaded eradication by the immune system. Its chronic interaction with the immune system and the ubiquitous presence worldwide makes H. pylori an ideal candidate to study as a trigger of autoimmune phenomena. In this review, we would present data regarding the interplay between H. pylori and various components of the immune system and its association with various autoimmune diseases.
  
  
  RESULTS
  Strong associations of H. pylori with some autoimmune diseases such as immune thrombocytopenia have been found; but most other autoimmune disease studies have revealed conflicting data. The chronic survival of H. pylori in humans is possible because of an overall downregulation of the body's immune response. In addition to this overall effect on the immune system, there are clinical and epidemiological data suggestive of H. pylori infection having a protective role in some autoimmune diseases.
  
  
  CONCLUSIONS
  Based on our review H. pylori status should be checked and treated only in certain autoimmune diseases such as ITP. For the majority of the autoimmune diseases, the role of H. pylori remains controversial signifying need for further research.
authors.affiliation: National Institute of Arthritis, Musculoskeletal and Skin Diseases, Bethesda, Maryland, USA. hasnisa@mail.nih.gov
authors.forename: Sarfaraz Ahmed
authors.initials: SA
authors.lastname: Hasni
mesh_terms: D001327:Autoimmune Diseases / Q000276:immunology / Q000382:microbiology* / Q000517:prevention & control; D016481:Helicobacter Infections / Q000150:complications* / Q000276:immunology; D016480:Helicobacter pylori; D006801:Humans; D007113:Immunity, Innate; D016553:Purpura, Thrombocytopenic, Idiopathic / Q000382:microbiology