Transcriptional programs of lymphoid tissue capillary and high endothelium reveal control mechanisms for lymphocyte homing

Lymphocytes are recruited from blood by high-endothelial venules (HEVs). We performed transcriptomic analyses and identified molecular signatures that distinguish HEVs from capillary endothelium and that define tissue-specific HEV specialization. Capillaries displayed gene programs for vascular development. HEVs were enriched in genes for immune defense and lymphocyte migration. We identify capillary and HEV markers and candidate mechanisms for regulated lymphocyte recruitment including a lymph node HEV-selective transmembrane mucin; transcriptional control of functionally specialized carbohydrate ligands for lymphocyte L-selectin; HEV expression of molecules for transendothelial migration; and metabolic programs for lipid mediators of lymphocyte motility and chemotaxis. We also elucidate a carbohydrate recognition pathway that targets B cells to intestinal lymphoid tissues, defining CD22 as a lectin-homing receptor for mucosal HEVs.