Helicobacter pylori: Bacterial Factors and the Role of Cytokines in the Immune Response Tania Beatriz Romero-Adria ´n • Jorymar Leal-Montiel • Francisca Monsalve-Castillo • Edgardo Mengual-Moreno • Ernesto Garcı ´a McGregor • Lenis Perini • Ana Antu ´nez Received: 8 August 2009 / Accepted: 25 September 2009 / Published online: 22 October 2009 Ó Springer Science+Business Media, LLC 2009 Abstract Helicobacter pylori is a gram-negative micro- aerophilic bacterium that is widely distributed geographi- cally and causes chronic gastritis, peptic ulcers, gastric adenocarcinoma, and mucosa-associated lymphoid tissue lymphoma. Bacterial virulence factors play an important role, since the virulent strains are more aggressive and increase the risk of developing severe clinical manifesta- tions; in addition, other determinant factors are the nutri- tional state and the immune response of the host. Studies on humans, non-human primates, and rodents have repor- ted that regulating proteins of the Th1 phenotype pre- dominate in the immune response to the bacterial infection. The cytokines produced by this phenotype, are not very effective in eradicating the microorganism and further- more, contribute to gastro-duodenal pathogenesis. Gastric inflammation in patients infected with H. pylori has been characterized by increased production of IL-1, IL-6, IL-12, IL-18, TNF-a, and IFN-c. Many prophylactic and therapeutic strategies have been researched using experi- mental animals. The utilization and effectiveness of vac- cination on humans requires more study. Introduction Helicobacter pylori (H. pylori) shows variations in its geographical distribution, and the diseases induced by the microorganism are more frequent in adults and individuals of advanced age. On a world level, prevalence of the infection in children varies between 10 and 80%. The lowest has been found in northeast Europe, Japan, and other parts of Asia, whereas the highest in India, Bangla- desh, and some cities of Africa and Latin America. In the Waro communities of Venezuela, seroprevalence of the infection was 38% in children and 84% in their mothers and is related to the precarious sanitary and hygienic conditions of these populations [1, 2]. It has been demonstrated that more than 80% of those infected remain asymptomatic. The development of clini- cal entities such as gastro-duodenal ulcer, gastric adeno- carcinoma, and primary gastric lymphoma depends on the inherent properties of the bacterial strain, the genetic pre- disposition, and the immunological response of the host, concurrent infections (protozoa), and infestations (hel- minths), among other factors [3–5]. Helicobacter pylori is a gram-negative micro-aerophilic bacterium, whose habitat is the gastric epithelium. It is located around intercellular epithelial connections and on the surface by producing special adherence structures called ‘‘bridge attachment.’’ In general, H. pylori is con- sidered non-invasive; nevertheless, in vitro, the capacity to invade gastric epithelial cells has been observed and in vivo, its location in the stomach of monkeys and humans, T. B. Romero-Adria ´n Á J. Leal-Montiel Á E. Mengual-Moreno Graduate Studies in Immunology, Faculty of Medicine, University of Zulia, Maracaibo, Venezuela T. B. Romero-Adria ´n(&) Á J. Leal-Montiel Á E. Mengual-Moreno Institute of Biological Research, Faculty of Medicine, University of Zulia, 69 B Avenue 77-49 Street, Panamericano Sector, Maracaibo, Venezuela e-mail: betrizromero@cantv.net F. Monsalve-Castillo Bioanalisis School, Faculty of Medicine, University of Zulia, Maracaibo, Venezuela e-mail: Monsalve22000@hotmail.com E. G. McGregor Á L. Perini Á A. Antu ´nez Rheumatology Unit, Central Hospital ‘‘Dr. Urquinaona’’, Maracaibo, Zulia, Venezuela 123 Curr Microbiol (2010) 60:143–155 DOI 10.1007/s00284-009-9518-4