Figure 3

The fusion proteins PinX1C–G₄S–9R–G₄S–mBAFF and PinX1C–9R–mBAFF selectively induce growth inhibition of BAFF receptor-expressing cells. (A) Cell proliferation assay was performed using the [³H]-thymidine incorporation method. BAFF receptor-expressing cells including Raji (a), Namalwa (b), Daudi (c), JeKo-1 (d) and THP-1 (e), and BAFF receptor-negative Jurkat cells (f) were seeded into a 96-well flat-bottom plate (1 × 10⁴ cells per well) and treated in triplicate with the fusion proteins at various concentrations. Thereafter, the cells were incubated for 5 days and [³H]-thymidine was added to the wells (1 μCi/well) during the last 16 h of incubation. Subsequently, the cells were collected on glass fiber filters, washed, dried and counted using standard scintillation methods, and percentages of the inhibition of proliferation were calculated. (B) Blocking assay was conducted to confirm the importance of the fused mBAFF for the activity of the fusion proteins. Raji cells were pretreated with 10 μg/ml of mBAFF for 1 h, followed by treatment with 250-nM of the fusion proteins in quadruplicate wells. The cells were then incubated for 5 days, and proliferation assays measuring [³H]-thymidine incorporation were conducted. DHFR, which does not bind BAFF receptors, serves as a negative control. All data in A and B are expressed as mean±s.e.