Radioimmunoassay versus flow cytometric assay to quantify LPS-binding protein (LBP) concentrations in human plasma

LPS-binding protein (LBP) is an acute phase protein present in plasma, that has been shown to play a major role in sensitizing monocytes to LPS. We describe here two assays to quantify LBP in plasma. The first assay made use of monophosphoryl lipid A to capture LBP in human plasma, and LBP was detected by radiolabeled anti-LBP IgG. The second assay measured LBP by flow cytometry, using LBPs ability to present LPS to the CD14 receptor present on monocytes. Both assays had a similar level of sensitivity, that allowed the quantification of LBP in human plasma.