Objective: To identify antigens of Chlamydia trachomatis recognized by synovial T cell clones from patients with reactive arthritis (ReA).
Methods: C. trachomatis specific T cell clones were isolated from synovial fluid of 2 patients with chlamydia induced ReA. The particular antigens/epitopes recognized by these clones were identified using T cell immunoblotting and testing recombinant chlamydial proteins and synthetic peptides.
Results: Two sets of clones were shown by immunoblotting to recognize antigens of roughly 60 and 18 kilodaltons (kDa) respectively. By testing recombinant chlamydial proteins these antigens were identified as the 57 kDa heat shock protein and the 18 kDa histone-like protein, Hc1. Mapping the epitope in Hc1 using synthetic peptides identified a peptide containing a sequence motif compatible with binding to HLA-DR1, the restricting antigen for the Hc1 specific clones.
Conclusion: These are the first 2 chlamydial antigens to be identified as targets of the synovial T cell response in chlamydia induced ReA. Both have properties that are shared with target antigens identified in ReA induced by enteric infection and relevant to the pathogenesis of joint inflammation.