Lymph nodes are instructed via the lymph about ongoing events in tissues both during the steady state and under provoked inflammation. In order to probe for tissue-to-node transduction mechanisms, we have developed a novel in vivo technique of pseudo-afferent lymph collection from the oro-nasal mucosae which represent the main portals of entry of micro-organisms and efficient routes for vaccination. After lateral lymph node resection of the head, a network of lymph ducts was reconstructed as checked by lymphography. Subsequent catheterization of the cervical lymph duct allowed the collection of cells that were shown to originate from the oro-nasal mucosae. These cells included dendritic cells, monocytes, granulocytes, memory CD45RAneg CD2pos integrin h7lo CD4 T cells, CD25pos CD4, CD8, g/y T cells, and B lymphocytes. This approach, which permits lymph collection over several weeks, opens a valuable and unique way to study leukocyte and particulate (microorganisms, vaccines) trafficking from head tissue to nodes under homeostastic and immuno-stimulatory conditions in a highly physiological setting.