Anti-Yersinia antibodies (IgA/IgG) in Campylobacter antibody-negative sera were found in 3–18 %/3–5 % of AE, 12–19 %/7–9 % of GBS, 10–12 %/6–14 % of RA, and 5–10 %/8–13 % of IBD sera. This evidence concerns the gene CD79A and inflammatory bowel disease.