Endotoxin receptor site. I. Binding of endotoxin to platelets.

Binding of bacterial endotoxin to platelets, erythrocytes, lymphocytes and granulocytes was examined by using diffusion dialysis. Platelets, erythrocytes, lymphocytes and granulocytes were fractionated from normal human blood and the binding of endotoxin (LPS: Lipopolysaccharide of E. coli) to each cell fraction was measured at 4 degrees C and the binding efficiency was expressed as a binding index (%d4degreesC +/- SD). The binding index for each cell fraction was as follows; 10.2 +/- 1.6 for platelets, 1.0 +/- 0.9 for erythrocytes, 4.3 +/- 1.6 for lymphocytes and 10.0 +/- 1.5 for granulocytes (n = 11) respectively. Since a platelet possesses a small cell surface area compared with other cells, it was clear that the endotoxin bound preferentially to platelets in vitro. The binding mechanism to the platelet cell surface was suggested to be direct binding of endotoxin to the receptor on platelet cell membrane rather than through an immunologically activated mechanism.