V4+ T Cells: A Novel IL-17-Producing T Subsets during the Early Phase of Chlamydial Airway Infection in Mice.

Our previous studies showed that T cells provided immune protection against Chlamydial (Cm), an obligate intracellular strain of chlamydia trachomatis, lung infection by producing abundant IL-17. In this study, we investigated the proliferation and activation of lung T cell subsets, specifically the IL-17 and IFN production by them following Cm lung infection. Our results found that five T cell subsets, V1+ T, V2+ T, V4+ T, V5+ T, and V6+ T, expressed in lungs of naïve mice, while Cm lung infection mainly induced the proliferation and activation of V4+ T cells at day 3 p.i., following V1+ T cells at day 7 p.i. Cytokine detection showed that Cm lung infection induced IFN secretion firstly by V4+ T cells at very early stage (day 3) and changed to V1+ T cells at midstage (day 7). Furthermore, V4+ T cell is the main T cell subset that secretes IL-17 at the very early stage of Cm lung infection and V1+ T cell did not secrete IL-17 during the infection. These findings provide in vivo evidence that V4+T cells are the major IL-17 and IFN-producing T cell subsets at the early period of Cm lung infection.