Figure 3

SpA impairs CXCR4 expression and CXL12-induced B-cell chemotaxis. (A) B cells were incubated with medium alone or 10 µg/mL Mod-SpA for 2 h at 37°C before staining with CXCR4-PE mAb. One representative experiment of 13 is shown. (B) B cells were incubated with medium alone (open bars) or 10 µg/mL Mod-SpA (black bars) for 0.5 to 24 h at 37°C before staining with CXCR4-PE mAb. Data are expressed as the mean ± SEM percentage of MFI values for residual surface CXCR4 expression obtained from two donors. (C) B cells were incubated with medium, 100 ng/mL CXCL12 or 10 ng/mL Mod-SpA for 2 h at 37°C before staining with CXCR4-PE mAb. Results are expressed as the mean ± SEM percentage of MFI values for residual surface CXCR4 expression obtained from 13 different donors. Two-tailed Wilcoxon test was used to determine statistical significance, and p values are indicated as *p < 0.05; **p < 0.01; ***p < 0.001. (D) B cells were incubated with medium alone, 10 µg/mL anti-IgM Ab or Mod-SpA for 16 h at 37°C before staining with CXCR4-PE mAb. Results are expressed as the mean ± SEM percentage of MFI values for residual surface CXCR4 expression obtained from seven different donors. Two-tailed Wilcoxon test was used to determine statistical significance and p values are indicated as *p < 0.05; **p < 0.01; ***p < 0.001. (E) B cells were incubated with medium alone, 10 µg/mL anti-IgM Ab or Mod-SpA for 16 h at 37°C. Medium, anti-IgM Ab and Mod-SpA-treated B cells were analyzed for migration to 100 ng/mL CXCL12. Results are expressed as the mean ± SEM percentage of specifically migrating cells obtained from 11 different donors. Two-tailed Wilcoxon test was used to determine statistical significance, and p values are indicated as *p < 0.05.