Guidelines for the assessment of high endothelial venule functionality and health.

High endothelial venules (HEVs) are specialized blood vessels that act as the entry point for lymphocytes into the lymph node. These vessels have a unique cuboidal morphology and modified sugar coating, which favors the entry process. A major challenge in studying these vessels is that isolating and culturing them leads to the loss of their phenotype, making in vivo assessment the only reliable method for their examination. Moreover, there is a current need for consensus guidelines to assess alterations in HEVs. Therefore, we have developed a manual for the assessment of HEV alterations under stress, such as during inflammation or lymph node metastasis, at the protein level via immunofluorescence staining and at the RNA level via single-cell RNA sequencing.