Capture of LPS by the complete human blood clot (platelet thrombus and fibrin clot)1.

1LPS was added to a suspension of platelet-rich plasma at the concentrations indicated in column 1, after which the suspension was induced to clot by the addition of LPS-free recombinant thrombin. After a 1 h incubation at 37°C, the clot was removed and the serum was diluted in LPS-free water as indicated in column 2, heated for 10 min at 70°C to inactivate endogenous inhibitors of the LAL test (presumably α2-macroglobulin), and assayed by the LAL test (column 3), as described in Materials and Methods. The sensitivity of the assay was 0.1 ng/mL LPS, but due to the dilution of the experimental samples, the maximum concentration of free LPS remaining in solution in the serum was correspondingly elevated, as indicated in column 4. Subtraction of the maximum free concentration of LPS from the initial concentration yields the minimum amount of LPS captured by 1 mL of platelet-rich plasma (column 5). This is our sole trial for this condition and serves as a replicate for data reported previously by Levin et al [28].