MONOCLONAL-ANTIBODY TO HEPARAN-SULFATE FROM AUTOIMMUNE TIGHT-SKIN (TSK) MICE BINDS TO THE ENDOTHELIAL-CELL SURFACE

Heparan sulfate proteoglycans have pleiotropic functions in the normal vasculature. Autoimmunity to heparan sulfate may play a role in vascu lar injury. In this study, monoclonal antibody (mb) 28C3-1 to heparan sulfate derived from autoimmune Tight skin (TSK) mice was investigated for its reactivity with endothelial cells. Mb 28C3-1 was previously d emonstrated to inhibit the heparin-accelerated formation of antithromb in III-thrombin complexes. In the current studies it is shown that mAb 28C3-1 bound to heparan sulfate proteoglycan with the highest affinit y in direct binding solid phase radioimmunoassay. Binding to the hepar an sulfate was stronger than binding to the protein core, indicating t hat the primary epitope of 28C3-1 is the polysaccharide component. Usi ng confocal fluorescent microscopy, mAb 28C3-1 was demonstrated to bin d to the endothelial cell surface. Furthermore, treatment of endotheli al cells with heparitinase abolished mAb 28C3-1 binding. These studies support the hypothesis that naturally occurring anti-heparan sulfate autoantibodies from autoimmune mice may cause vascular injury by initi al interaction with endothelial cell surface heparan sulfate.