FIGURE 2.

Induction of CD86 by IL-21 requires direct signaling to B cells and is dependent on protein neosynthesis. (A) BALB/c CD4⁺CD25⁻ conventional T cells (2.5 × 10⁴) were cultured with 2.5 × 10⁴ CD19⁺ B cells for 16 h alone or in the presence of 200 ng/ml IL-21. Cell populations were deficient for the IL-21R as indicated. Plots show CD86 expression for gated CD19⁺ B cells. (B) BALB/c CD19⁺ B cells (1 × 10⁶) were cultured for 6 h alone, with 200 ng/ml IL-21, with 10 μg/ml cycloheximide, or both. Representative confocal microscopy images show CD86 staining. Scale bars, 10 μm. (C) Graph shows collated CD86 mean fluorescence intensity (MFI) for cells from (B) analyzed by flow cytometry. Data are representative of three independent experiments. (D) BALB/c CD19⁺ B cells (1 × 10⁶) were cultured for 16 h alone or in the presence of 200 ng/ml IL-21. Graph shows relative CD86 mRNA expression for cultured cells and freshly isolated CD19⁺ B cells. Data are representative of three independent experiments. **p < 0.01.