A significant positive correlation was found between C3 (r = 0.49, p < 0.0001), IgA (r = 0.25, p < 0.05), RF (r = −0.23, p < 0.05), and CRP (r = 0.40, p < 0.001) and BMI in the IBS group. The gene discussed is CD79A; the disease is irritable bowel syndrome.