Fig. 4.

Sialylation affects BCMA ligand-mediated protection from apoptosis induced by DEX. RPMI8226 cells pretreated with or without sialidase were treated with DEX in the absence or presence of APRIL or BAFF. Three days later, cells were subjected to annexin V staining by FACS analysis. (A) One representative result of three independent experiments is shown; the number in the dot plot indicates the percentage of annexin V–positive cells. (B) The mean value ± SEM of three independent experiments from A. (C) Percentage of rescue of apoptosis as determined by (% of apoptosis caused by DEX–% of apoptosis induced by DEX in the presence of BCMA ligand)/(% of apoptosis induced by DEX). (D and E) Histograms of FACS analysis show that removal of sialylation increases the binding of ligands for BCMA with cell surface. H929 or RPMI8226 cells were pretreated with sialidase and then incubated with Fc-APRIL (D) or Fc-BAFF (E), followed by detection with FACS analysis. The number in the histogram indicates the mean of fluorescence. Bar graphs below D and E show statistical analysis of ligand binding after treatment of cells with sialidase in three independent experiments. Results are mean ± SEM. *P < 0.05 and **P < 0.01.