MECA-79 recognizes a carbohydrate epitope shared with a group of sulfation decorated sialomucins, including sulfated ligands for CD62L (CD34, GlyCAM-1, Sgp200, and a subset of MAdCAM-1). This set antigens has been referred to as peripheral node addressin (PNAd) with the molecular mass 50-250 kD. It has been identified that GlcNAc-6-SO4 sulfation contributes to MECA-79 binding and the core 1 beta1,3-N-acetylglucosaminyltransferase is required for the generation of the MECA-79 epitope. MECA-79 is expressed on high endothelial venules (HEV) of lymphoid tissues, chronic inflamed tissues and rheumatoid synovia. The interaction of PNAd with CD62L receptor is involved in tethering and rolling of lymphocytes along HEV in lymphoid tissues. MECA-79 antibody reacts with Mouse, human and many other species PNAd and blocks L-selectin-dependent lymphocyte adhesion in vitro and in vivo.