Cutting Edge: Evidence for Nonvascular Route of Visceral Organ Immunosurveillance by T Cells.

Lymphocytes enter tissues from blood vessels through a well-characterized three-step process of extravasation. To our knowledge, nonvascular routes of lymphocyte entry have not been described. In this article, we report that Ag-experienced CD8 T cells in mice recirculate from blood through the peritoneal cavity. In the event of infection, Ag-experienced CD8 T cell subsets adhered to visceral organs, indicating potential transcapsular immunosurveillance. Focusing on the male genital tract (MGT), we observed Ag-experienced CD8 T cell migration from the peritoneal cavity directly to the infected MGT across the capsule, which was dependent on the extracellular matrix receptor CD44. We also observed that, following clearance of infection, the MGT retained functional resident memory CD8 T cells. These data suggest that recirculation through body cavities may provide T cells with opportunities for broad immunosurveillance and potential nonvascular mechanisms of entry.