KIR2DS4 and peptic ulcer disease: Examples of pathogenic bacteria that carry an epitope within RecA for HLA-C*05:01–restricted binding of KIR2DS4 include the following: H. pylori, an infectious agent associated with peptic ulcers and gastric cancers (44); bacteria of the Brucella genus, which cause a zoonotic infection called brucellosis (45); C. jejuni, a major cause of gastroenteritis with an incidence as common as that caused by Salmonella infections (46); and C. trachomatis, which is the most common sexually transmitted infection, with over 90 million cases annually worldwide (47).