The introduction of Freund's complete adjuvant into footpads of mice leads to functional changes of the high endothelial venules (HEV) in the draining lymph nodes. Using an in vitro adhesion assay, increased binding of monocytes and dendritic cells could be seen. These effects are also seen after injection of high doses of INF-gamma. No changes in the expression of vascular addressins, VCAM-1, E selection or ICAM-1 could be observed but the binding of monocytes could be blocked with an antibody against Mac-1. Depletion studies have made it clear that macrophages in the lymph node are not directly involved in the activation of the HEV. The induction of additional adhesion mechanisms on HEV could be an efficient way to recruit inflammatory cells into the lymph node, thereby regulating the local immune response.