INTERNALIZATION OF CHLAMYDIA BY DENDRITIC CELLS AND STIMULATION OF CHLAMYDIA-SPECIFIC T-CELLS

Chlamydia species are the causative agents of trachoma, various forms of pneumonia, and the most common sexually transmitted diseases, Altho ugh the infection cycle has been extensively characterized in epitheli al cells, where the Chlamydia entry-vacuoles avoid fusion with host-ce ll lysosomes, the cellular immune response has received less attention , Moreover, despite the abundant presence of dendritic cells (DC) in t he sites of infection, the interaction between Chlamydia and DC has ne ver been studied, We observe that DC kill Chlamydia trachomatis and Ch lamydia psittaci, The chlamydiae are internalized by the DC in a nonsp ecific manner through macropinocytosis, and the macropinosomes fuse su bsequently with DC lysosomes expressing MHC class II molecules, The in teraction induces maturation of the DC, since presentation of an exoge nous Ag is severely inhibited after a 1-day incubation, although chlam ydial Ags are still presented and recognized by Chlamydia-specific CD4 (+) T cells. Thus, DC most Likely play a role in initiating the T cell response in vivo and could potentially be used in adoptive transfer t herapies to vaccinate against Chlamydia.