| dc.description.abstract | CD4+ T helper (Th) cells search a vast tissue area to find sites of infection or inflammation. The distribution of Th cells in tissues is shaped by tissue architecture, chemotactic cues, adhesion molecules, and the location of antigen (Ag). How Th cells integrate these signals to optimize tissue entry, exploration, and correct positioning for delivery of effector function is poorly understood. To gain insight into the stages of Th cell migration, an optogenetic tool based on the photoconvertible Kaede protein was used to spatiotemporally mark or “timestamp” type 1 Th (Th1) cells in inflamed skin. The timestamp enabled analysis of Th1 cells that recently entered tissue, Th1s that spent >24 hours in tissue, and Th1s that exited to the draining lymph node. Flow cytometry analysis revealed distinct changes in surface chemokine receptors (CCRs), integrin receptors, and markers of costimulation and activation based on tissue dwell time. CCRs were upregulated in inflamed skin, with a surprising exception – the canonical Th1 CCR CXCR3 was rapidly lost upon tissue entry. In tissue, integrins were most upregulated after entry, and costimulatory receptors and activation markers were upregulated over time. Some of these changes occurred within 4 hours of tissue entry. Both non-Ag signals and encounters with cognate Ag influenced receptor expression. These data suggest that one set of proteins is utilized in tissue entry while another combination is used to traffick through the skin or remain in tissue. The spatiotemporal sequence uncovered by this work may point to novel therapeutic targets, which could be manipulated to enhance or regulate Th cell effector function in treatments for infection, inflammation, and cancer. | |
