CD8⁺T cell immunosurveillance dynamics influence the outcome of intracellular infections and cancer. Here we used two-photon intravital microscopy to visualize the responses of CD8⁺resident memory T cells (T_RMcells) within the reproductive tracts of live female mice. We found that mucosal T_RMcells were highly motile, but paused and underwent in situ division after local antigen challenge. T_RMcell reactivation triggered the recruitment of recirculating memory T cells that underwent antigen-independent T_RMcell differentiation in situ. However, the proliferation of pre-existing T_RMcells dominated the local mucosal recall response and contributed most substantially to the boosted secondary T_RMcell population. We observed similar results in skin. Thus, T_RMcells can autonomously regulate the expansion of local immunosurveillance independently of central memory or proliferation in lymphoid tissue.

• Nature Immunology(2018)

doi:10.1038/s41590-017-0029-3