Reaction of toxic shock syndrome toxin 1 with endothelium of human umbilical cord vein.

The binding of toxic shock syndrome toxin 1 (TSST-1) to the endothelium of human umbilical cord veins and arteries was studied. Radiolabeled TSST-1, perfused through a segment of human umbilical cord vein, bound to the vessel at 4 degrees C, with a dissociation constant (Kd) of 6.5 X 10(-10) M. A pre-embedding electron-microscopic immunogold technique revealed that TSST-1 was located in the veins and arteries on the surface of endothelial cells and in the area of cell contacts. Umbilical cord vein segments filled with TSST-1 were incubated for 30 minutes at 37 degrees C, fixed by perfusion and embedded in hydrophilic resin (Lowicryl K4M). Postembedding immunogold staining of ultrathin sections showed TSST-1 in the vesicles crossing the cytoplasm of the veins' endothelial cells and entering underlying elastic and collagen layers.