Peripheral blood T cell proliferative response to chlamydial organisms in gonococcal and non-gonococcal urethritis and presumed pelvic inflammatory disease

Objective: To study peripheral blood mononuclear cell (PBMC) proliferative response to Chlamydia trachomatis elementary bodies in (a) controls, (b) va rious stages of gonococcal (c) and non-gonococcal urethritis, and (d) women with a clinical diagnosis of pelvic inflammatory disease (PID). Methods: We categorised 102 men presenting to a GUM clinic with urethritis by organisms (C trachomatis (CT) or Neisseria gonorrhoeae (NG) (both by cul ture), and whether it was their first (urethritis naive) or subsequent (ure thritis experienced) attack. 23 women presenting to the clinic with a clini cal diagnosis of PID were also investigated. We measured PBMC proliferative responses to C trachomatis (DK20-an oculogenital strain, serovar E), lysat e of McCoy cells (used to propagate chlamydiae), and the recall antigen PPD . Controls were 37 men and women without present or past history of urethri tis or chlamydial infection. Results were expressed as the ratio of the sti mulation index (SI) obtained with DK20 compared with McCoy cells (DK index) , and the ratio of the SI obtained with DK20 compared with PPD (PPD index). Results: The median SI to DK20 in the urethritis was 12.7 which was signifi cantly higher than the controls (7.6, p <0.003). The median SI to the recal l antigen PPD was similar in the urethritis patients (17.4) and the control s (22.4). All urethritis patient subgroups had a significantly higher DK in dex and PPD index than the controls. There was no difference in the PPD and DK index between urethritis naive and urethritis experienced patients and between the culture positive and culture negative urethritis subgroups. In PID patients only the PPD index was significantly higher than the controls. Conclusion: Men presenting with urethritis and women presenting with PID bo th have significantly greater peripheral blood mononuclear cell proliferati ve responses to the DK20 strain of C trachomatis than controls. A similar T cell proliferative response pattern in urethritis naive patients with eith er gonococcal or non-gonococcal urethritis could be because low sensitivity of CT culture failed to diagnose some cases of C trachomatis. However, it may also signify earlier exposure of the patients to chlamydial antigens (f or example, C pneumoniae), cross reacting antigens such as heat shock prote ins from other microbial species, or a "bystander" activation of chlamydia specific memory T cells trafficking through mucosal lymphoid tissue during urethritis. These results suggest evidence of T cell mediated response to C trachomatis cannot be used as a diagnostic tool.