150-P: POLYMORPHISM OF MICA IN HELICOBACTER PYLORI-POSITIVE MEXICAN PATIENTS WITH GASTRODUODENAL LESIONS

Abstract

MHC class I chain related gene A (MICA) is a highly polymorphic gene expressed in gastrointestinal epithelial cells. MICA activates NK and gamma delta T cells trough the binding of NKG2D receptor under cellular stress situations (infection or transformation). Helicobacter pylori (H. pylori) colonization of the gastric mucosa is a major cause for chronic gastritis and predisposition for peptic ulcer and gastric cancer. We analyze the associations between allelic and microsatellite polymorphism of MICA, and gastroduodenal lesions related to H. pylori infection in Mexican Mestizo patients. We genotyped by RSCA technique 282 H. pylori-positive patient samples diagnosed by endoscopy and histology (non-atrophic gastritis=139, intestinal metaplasia=67, gastric cancer=34 and duodenal ulcer=42), and 96 H. pylori seropositive asymptomatic persons without gastric lesions. The allelic and microsatellital frequencies in the different groups of patients were statistically compared by chi-square and Fisher test (pc < 0.05). We found in the asymptomatic group five microsatellites: A4 (5.8%), A5 (25.2%), A5.1 (10.7%), A6 (18.0%) and A9 (40.3%) and six MICA alleles: ∗001 (5.2%), ∗00201 (40.6%), ∗004 (17.2%), ∗00801 (10.9%), ∗010 (25.0%) and ∗011 (1.1%). In patients we observed a decrease of the 00201/00201 genotype frequency in duodenal ulcer (9.5%) when compared with non-atrophic gastritis (20.0%) and asymptomatics (23.0%), but it was not statistically significant. We did not find any association with gastric cancer. These results strongly suggest that the MICA polymorphism may not be associated with the gastroduodenal diseases provoked by H. pylori infection in Mexican population. (CONACyT 6957, FOFOI 2001/007 and 2002/110).