 This tight binding stops further movement of the T cell which can then move between HEV cells into the lymph node by a process termed 'diapedesis' (or extravasation).Despite intensive efforts, few HEV-specific markers have been described.The best HEV marker currently available is a carbohydrate epitope recognized by the monoclonal antibody (mAb) MECA-79, which stains all HEVs within lymphoid tissues and does not react with postcapillary venules or large vessels in spleen, thymus or nonlymphoid tissues.