Figure 6. CR3, partially activated by TLR2 inside-out signaling, is critical for Schu S4 phagocytosis by hMDMs.

(A) hMDMs were transfected with scrambled siRNA or siRNAs targeting CD11b or TLR2. 48 hrs later, the level of CD11b and TLR2 were examined by Western blot. (B) CD11b knockdown was also examined by immunofluorescence microscopy with mouse CD11b (M1/70) antibody. Nuclei were stained with DAPI. (C) 48 h after siRNA transfection hMDMs were infected with non-opsonized or serum pre-opsonized Ft Schu S4 in the absence of serum for 15 min. Infected cells were subjected to differential staining of extracellular (yellow or green) and intracellular (red) bacteria. Representative images are shown from 3 independent experiments. (D) Bacterial uptake was quantified as the number of bacteria that are inside or attached per cell. At least 300 cells were counted for every sample. Data are representative of 3 independent experiments performed in triplicate (mean ± SD). * p<0.05, compared with control siRNA samples (1-Way ANOVA and Tukey's Multiple Comparison Test).