Indirect evidence of intra-articular immunoglobulin G synthesis in patients with Chlamydia trachomatis reactive arthritis

Objectives. To investigate whether B-cell stimulation occurs in joints of C hlamydia trachomatis reactive arthritis patients by comparing the immunoglo bulin G (IgG) anti-C trachomatis antibody responses in serum and synovial f luid (SF). Methods. The number and spectrum of C trachomatis antigens recognized by pa ired serum and SF samples from 16 patients with C trachomatis reactive arth ritis and 20 patients with other inflammatory arthropathies independent of this bacteria, were studied by immunoblotting. The responses to five differ ent Chlamydia antigens were also determined in enzyme-linked immunosorbent assays. Results. In C trachomatis reactive arthritis patients, a higher number of C trachomatis antigens was recognized by SF (17.6 +/- 5.1) than by serum (11 .1 +/- 6.3) IgG and a higher intensity of SF IgG binding to the outer membr ane protein 2 (OMP2) was observed. Conclusions. These results suggest an intra-articular IgG production and a possible role of some Chlamydia antigens like OMP2 in the pathogenesis of C trachomatis reactive arthritis.