PolyP inhibits C4d deposition on endothelial cells in a concentration-dependent manner. HMEC-1 were exposed to (A) NHS, (B) MBL-deficient serum, or (C) C1q-deficient serum in the presence of varying concentrations of polyP130 (P130) or monoP (P1). For each serum, a corresponding HIS control was tested (flow cytometry graphics on right panels). After 1 hour, the reactions were stopped, and C4d deposition was quantified by flow cytometry. Data shown are representative of 3 independent experiments for each serum condition. Histograms on the left show normalized MFI levels of C4d deposited on endothelial cells. Percent MFI values are mean ± SEM of duplicates. On the right, flow cytometry graphic reveals inhibition of C4d deposition, reflected by reduced fluorescence. HIS, heat-inactivated serum; MFI, mean fluorescence intensity; SEM, standard error of the mean.
