Circulating immunity protects the female reproductive tract from Chlamydia infection

Significance Sexually transmitted infections are widespread and cause irreparable harm to young women. After infection of the female reproductive tract, lymphoid clusters are generated with fully resident lymphocytes that do not recirculate via blood or lymphatic vessels. However, the protective value of tissue-resident lymphocytes or cluster formation has not been determined for important reproductive pathogens. Our study demonstrates that these local immune structures are unnecessary for robust protective immunity toChlamydia . Instead, efficient tissue surveillance is provided by circulating memory lymphocytes generated outside reproductive tissues. These findings reinforce the value of assessing circulating, rather than local, immune parameters ofChlamydia immunity and suggest that future vaccine efforts should focus on the elicitation of robust systemic immunity to provide local mucosal protection.