HP and duodenal ulcer: DQA1*0201 allele associated with the high CD risk was significantly rarer in the HP-positive duodenal ulcer patients than in the HP-negative controls (Azuma et al., 1995; Lionetti et al., 2014). HLA-DRB1*0301 and DRB1*07 associated with high CD risk in some ethnic groups are involved in the of some HPproteins recognition and in subsequent activation of gastric T cells within the framework of antiinfective immune response (Bilbao et al., 2002; talová et al., 2002; Bergman et al., 2005).