Intra-articular chlamydial antigen and inflammatory arthritis.

Joint material from 133 patients with well-characterized inflammatory arthritis, including individuals likely to have suffered reactive arthritis, was studied. The majority of patients were also examined for the presence of genital tract infection with Chlamydia trachomatis. Fluorescein-conjugated monoclonal antibodies demonstrated the presence of C. trachomatis antigen in synovial fluid cell deposits or synovial sections from inflamed knee joints of seven patients with reactive arthritis. The significance of these findings is discussed, as is the low rate of detection of chlamydial antigen in either the genital tract or the joint from patients in this study. We emphasize the need for further work aimed at identifying the relevant immunogenic chlamydial antigens responsible for the initiation of reactive arthritis.