Characterization of Pathogenic CD8⁺ T cells in Chlamydia-Infected OT1 Mice

Chlamydia trachomatis is a leading infectious cause of infertility in women due to its induction of lasting pathology such as hydrosalpinx. Chlamydia muridarum induces mouse hydrosalpinx because C. muridarum can both invade tubal epithelia directly (as a first hit) and induce lymphocytes to promote hydrosalpinx indirectly (as a second hit). In the current study, a critical role of CD8¹ T cells in chlamydial induction of hydrosalpinx was validated in both wild type C57BL/6J mice and OT1 transgenic mice. OT1 mice failed to develop hydrosalpinx partially due to the failure of their lymphocytes to recognize chlamydial antigens. CD8¹ T cells from naive C57BL/6J mice rescued the ability of recipient OT1 mice to develop hydrosalpinx when naive CD8¹ T cells were transferred at the time of infection with Chlamydia. However, when the transfer was delayed for 2 weeks or longer after the Chlamydia infection, naive CD8¹ T cells no longer promoted hydrosalpinx. Nevertheless, CD8¹ T cells from mice immunized against Chlamydia still promoted significant hydrosalpinx in the recipient OT1 mice even when the transfer was delayed for 3 weeks. Thus, CD8¹ T cells must be primed within 2 weeks after Chlamydia infection to be pathogenic, but, once primed, they can promote hydrosalpinx for .3 weeks. However, Chlamydia-primed CD4¹ T cells failed to promote chlamydial induction of pathology in OT1 mice. This study optimized an OT1 mouse-based model for revealing the pathogenic mechanisms of Chlamydia-specific CD8¹ T cells.