Avidity of anti-Yersinia antibodies in yersiniosis patients with and without Yersinia-triggered reactive arthritis.

Avidity of IgM, IgG, and IgA class anti-Yersinia antibodies was compared in sera of 22 patients with yersiniosis and subsequent reactive arthritis versus sera of 22 patients without postinfection complications. An enzyme-linked immunosorbent assay was used for antibody determination. Less than 2 months after onset of the infection, the patients with arthritis had fewer high-avidity IgM antibodies against the bacterial lipopolysaccharide (P = 0.035) and more high-avidity IgA antibodies against bacterial cell extract (P = 0.039) than did the patients without arthritis. This difference increased with time.