Evidence of Cellular Immune Response to Outer Membrane Protein ofSalmonella typhimuriumin Patients with Enthesitis-related Arthritis Subtype of Juvenile Idiopathic Arthritis

Abstract

Objective.Enthesitis-related arthritis subtype of juvenile idiopathic arthritis (JIA-ERA) clinically resembles reactive arthritis (ReA). In patients with ReA the immune response is targeted at the outer membrane protein (OMP) ofSalmonella typhimurium. We studied the immune response in JIA-ERA toS. typhimuriumOMP.Methods.Synovial fluid mononuclear cells (SFMC) and peripheral blood mononuclear cells (PBMC) were isolated from blood and SF of patients with JIA-ERA. Lymphocyte transformation test was done withS. typhimuriumOMP and crude bacterial lysates ofYersinia enterocolitica,Shigella flexneri, andS. typhimurium. IgG and IgA ELISA were performed in serum and SF usingS. typhimuriumOMP as antigen and compared with sera from healthy controls.Results.In PBMC samples (n = 25) an antigen-specific proliferative response was seen in 13 patients and a cross-reactive response in 6. Among these 19 patients, 12 showed response to OMP. In SFMC (n = 15) antigen-specific responses were seen in 3 patients and cross-reactive responses in 9. Among these 12 patients, 11 showed response to OMP. The IgG and IgA anti-OMP antibody concentrations in serum and SF were similar in patients and controls.Conclusion.In JIA-ERA, OMP is the major antigenic target recognized by both SFMC and PBMC. Response to OMP is independent of specific bacterial response, suggesting that OMP is the immunodominant antigen. In these patients, absence of significant humoral response suggests response to OMP is mainly T cell mediated.