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

Figure 3

Lp(a) opsonized NTHi for phagocytosis by U937 macrophages. (a, b) The phagocytosis of NTHi49247, NTHi49766, E.coli BL21, and E.coli JM109 by U937 macrophages was estimated by CFU counts and RFI measurements after a (a) 120 or (b) 160 min incubation. Efficiency of phagocytosis is indicated with the following formula: , where is the value of bacteria with or without treatment after the indicated incubation period in culture and is the value of bacteria with the same treatment and incubation period as that of but with coincubation with macrophages. The relative phagocytosis efficiency of protein-treated bacteria was calculated by using the protein-free control group in the same experiment as a benchmark. Raw fluorescence measurements were corrected using a buffer blank. Each experiment was conducted at least in triplicate. Data are shown as . Statistical significance of samples with bacteria+Lp(a) versus bacteria+LDL was determined by two-way ANOVA with the Bonferroni post hoc test (, ). (a, b) The CFU and RFI values at two time points of the macrophages phagocyting Lp(a)-treated NTHi49247 and NTHi49766 were significantly higher than those of the cells phagocyting LDL-treated microbes. And for two strains of E.coli, there was no significant difference in CFU and RFI values of the cells engulfing Lp(a)-treated and LDL-treated microbes. (c) Change of phagocytosis efficiency of NTHi49247 in the presence of rKIV₁₀, LDL, BSA. No significant differences among those three treatments. (d) Lp(a) promotes the internalization of NTHi49247 into U937 macrophages. Along with the significant increased phagocytosis of NTHi49247-Lp(a) by U937 macrophages, the intracellular viable NTHi49247 in U937 macrophages is significantly increased. Statistical significance of samples with bacteria+Lp(a) or LDL versus bacteria alone was calculated by two-way ANOVA with the Bonferroni post hoc test (, ).

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