Background
CCL21 expression in secondary lymphoid organs is instrumental in mediating L-selectin+ CCR7+ naive T-cell and B-cell recruitment from the bloodstream via PNAd+ high endothelial venules (HEV). CCL21 is also constitutively produced by lymphatic vessels functioning as a recruiting factor for CCR7+ mature dendritic cells from peripheral tissues to regional lymphoid organs. The same factor participates to the inflammatory cascade being associated with lymphoid neogenetic events and being upregulated in peripheral lymphatic vessels, increasing the magnitude of T-cell response by favouring dendritic cell recruitment to draining lymph nodes.