Analysis of the IgG subclasses (IgG1, IgG2, IgG3, IgG4) in patients with arthritis (n = 35) and uncomplicated yersiniosis (n = 49) showed that in patients with gastritis, the prevalence of IgG2 antibodies to Yersinia Yop proteins increased with age and was the highest after the age of 40. The gene discussed is IGHG3; the disease is Yersinia infectious disease.