Figure 4

PolySia does not affect basal phagocytosis and homeostatic endocytosis.

(a) Phagocytosis of microbeads as determined by flow cytometry. PolySia avDP20 did not change phagocytosis of microbeads. However, the LPS-induced increase in microbeads phagocytosis was antagonized by 0.5 μM and 1.5 μM polySia avDP20. The phagocytosis inhibitor cytochalasin D was used as control. Data are presented as mean +/− SEM of at least n = 3 independent experiments. **p < 0.01, ***p < 0.001; ANOVA followed by Bonferroni. (b) Phagocytosis of microbeads as determined by flow cytometry. Sia, oligoSia DP6 and polySia avDP20 did not change phagocytosis of microbeads. However, LPS-induced increase in microbead phagocytosis was antagonized by 1.5 μM polySia avDP20. The phagocytosis inhibitor cytochalasin D was used as control. Data are presented as mean +/− SEM of at least n = 3 independent experiments. *p < 0.05; **p < 0.01; ANOVA followed by Bonferroni. (c) Phagocytosis of microbeads by transduced THP1-derived macrophages as determined by flow cytometry. In control plasmid (Sh Control) transduced cells, polySia avDP20 was able to antagonize the effect of LPS on microbead phagocytosis. However, in SIGLEC11 knock-down plasmid (Sh SIGLEC-11) transduced macrophages, polySia avDP20 had no effect on LPS-induced microbead phagocytosis. The phagocytosis inhibitor cytochalasin D was used as control. Data are presented as mean +/− SEM of at least n = 3 independent experiments. * < 0.05; ANOVA followed by Bonferroni. (d) Endocytosis of nanobeads as determined by flow cytometry. PolySia avDP20 did not change the homeostatic basal nanobeads endocytosis. Furthermore, the inflammatory LPS-induced increase of nanobead endocytosis was not antagonized by polySia avDP20. The endocytosis inhibitor methyl-beta-cyclodextrin was used as control. Data are presented as mean +/− SEM of n = 3 independent experiments. ***p < 0.001; ANOVA followed by Bonferroni.