Objective: To dissect the host defense mechanisms in relation to the development of Yersinia-associated arthritis by evaluating the impact of tumor necrosis factor receptor p55 (TNFRp55) deficiency on Yersinia enterocolitica infection.
Methods: TNFRp55-/- and C57BL/6 mice were inoculated intravenously with arthritogenic strain 8081 of Yenterocolitica serotype 0:8. Mice were observed daily for generating survival curves and monitoring arthritis. In subsequent sets of experiments, mice were sacrificed at day 14 after infection for examination of histopathology of joints, bacterial clearance, macrophage microbicidal activity, nitric oxide (NO) production, oxidative burst generation, and cytokine production.
Results: There was an 80% mortality rate in TNFRp55-/- mice compared with 25% in the controls at 8 weeks after inoculation with 70 colony-forming units of Y. enterocolitica 0:8. Histologic examination of joint tissues revealed that TNFRp55-/- mice developed more severe arthritis, including cartilage degradation and bony destruction, than controls at day 14 after infection. The more extensive joint pathology in TNFRp55-/- mice was correlated with the higher bacterial load in liver, spleen, and lungs, and with the increased levels of interleukin-10. TNFRp55-/- mice displayed impaired intracellular killing of bacteria by macrophages. This was associated with decreased NO production and impaired oxidative burst activity.
Conclusion: This study demonstrates that TNF signaling through TNFRp55 controls the severity of Yersinia-induced arthritis and implicates TNF-mediated macrophage microbicidal activity as a central event in this process.