Antigen archiving by lymph node stroma: A novel function for the lymphatic endothelium

Secondary lymphoid stroma performs far more functions than simple structural support for lymphoid tissues, providing a host of soluble and membrane-bound cues to trafficking leukocytes during inflammation and homeostasis. More recently it has become clear that stromal cells can manipulate T-cell responses, either through direct antigen-mediated stimulation of T cells or more indirectly through the retention and management of antigen after viral infection or vaccination. In light of recent data, this review provides an overview of stromal cell subsets and functions during the progression of an adaptive immune response with particular emphasis on antigen capture and retention by follicular dendritic cells as well as the recently described "antigen archiving" function of lymphatic endothelial cells (LECs). Given its impact on the maintenance of protective immune memory, we conclude by discussing the most pressing questions pertaining to LEC antigen capture, archiving and exchange with hematopoetically derived antigen-presenting cells.