MECHANISMS OF LIPOPOLYSACCHARIDE-INITIATED RABBIT PLATELET RESPONSES .2. EVIDENCE THAT LIPID-A IS RESPONSIBLE FOR BINDING OF LIPOPOLYSACCHARIDE TO THE PLATELET

  • 1 January 1979
    • journal article
    • research article
    • Vol. 122  (3) , 753-758
Abstract
The mechanism of bacterial [Escherichia coli] lipopolysaccharide (LPS)-initiated, complement(C)- mediated rabbit platelet lysis was examined. Activation of the alternative C pathway is required for platelet lysis. Preparations of LPS that activate only the classical pathway (e.g., lipid A) do not cause lysis. The temporal relationship of the interaction of the LPS with the platelet before the addition of plasma suggests a time-dependent association of the LPS with the platelet. On the basis of inhibition with polymyxin B, treatment of LPS with alkali and blocking experiments with polysaccharide-free LPS preparations, the lipid A region of the LPS molecule is responsible for attaching the LPS to the platelet. A comparison of the activity of lipid A-associated protein(LAP)-LPS complexes with protein-free LPS demonstrated that an equivalent extent of platelet lysis was achieved with 1/100 the concentration of the former as that required for protein-free LPS. LAP facilitates attachment of the LPS to the platelet.