Lipoprotein(a), an Opsonin, Enhances the Phagocytosis of Nontypeable Haemophilus influenzae by Macrophages

Figure 2

Interactions between Lp(a) and bacteria were analyzed by ELISA and bacterial adherence assay. (a–d) Binding of Lp(a) to bacteria was analyzed by whole-cell ELISA. Purified Lp(a) or LDL was added to intact bacteria at increasing concentrations (0.05–5 μg/mL). The bound fraction of Lp(a) was measured using anti-apo(a) Ab, and that of LDL was measured using anti-LDL Ab. Lp(a) bound to each of the two strains of NTHi in a dose-dependent manner, whereas the negative control protein LDL did not (a, b). Two strains of E. coli showed weak binding to both Lp(a) and LDL (c, d). Data shown are mean values from three experiments conducted in duplicate, and error bars indicate SDs. Statistical significance was determined by two-way ANOVA and the Bonferroni post hoc test. , , and . (e) Attachment of NTHi to immobilized Lp(a) was visualized by light microscopy after standard gram staining. Wells, either coated or uncoated with BSA, were included as negative controls. Representative images of two independent experiments are shown.

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