Psophocarpus tetragonolobus agglutinin reveals N-acetyl galactosaminyl residues confined to endothelial cells and some epithelial cells in human tissues.

We studied the binding of Psophocarpus tetragonolobus agglutinin (PTA) conjugates to human adult tissues. In all kidney specimens studied, PTA bound in a blood group-independent way to endothelia in glomerular and intertubular capillaries as well as in larger vessels. In addition, a heterogeneous binding to collecting duct cells was seen. In specimens of human smooth, cardiac, and skeletal muscle, cerebellum, lung, thyroid gland, liver, proliferative endometrium, and placenta, PTA bound only to endothelial of capillaries and larger vessels. In epidermis and gingiva, PTA conjugates additionally revealed reactivity with keratinocytes. Similarly, in salivary gland, urinary bladder, gastrointestinal tract, mammary gland, and renal pelvis, PTA reacted with some epithelial cell layers. The PTA conjugates gave an even cell surface membrane staining of cultured umbilical vein endothelial cells. Lectin-affinity binding of radioactively surface-labeled endothelial cells showed that PTA and Ulex europaeus I agglutinin (UEA-I) recognized related major cell surface glycoproteins. The results with PTA conjugates show that certain N-acetyl galactosaminyl residues are, in addition to some epithelial cells, confined to endothelial cells in human tissues.