Fig. 9.

Human IgD^low/− B cells induce the proliferation of human Treg in vitro. Human splenic B cells (CD19⁺) (a) and IgD^low/− (CD19⁺CD20⁺CD24⁻IgD^low/−) B cells (a–c) and Treg (CD4⁺CD25^hi) were FACS purified and the Treg were labeled with CFSE. d Treg (0.5 × 10⁵) were cultured alone or with splenic B cells (1 × 10⁵) in the presence of anti-CD3 (2 mg/ml) and irradiated APC (CD4⁻CD8⁻CD19⁻) for 96 h. Each symbol represents a single human sample. **p < 0.01, no B cells vs. IgD^low/−. e Representative flow cytometry histograms with gating of proliferating cells is shown from one experiment of four from d. f Human peripheral blood B cells (CD19⁺), IgD^hi (CD19⁺CD20⁺CD24⁻IgD^hi) B cells, IgD^low (CD19⁺CD20⁺CD24⁻IgD^low/−) B cells, and Treg (CD4⁺CD25^hi) were FACS purified. CFSE-labeled Treg (0.5 × 10⁵) were cultured alone or with 1 × 10⁵ total B cells, IgD^hi, or IgD^low/− in the presence of plate bound anti-CD3 (10 mg/ml) and anti-CD28 (10 mg/ml). After culture, the cells were stained with CD4 and the percentage of proliferating Treg cells was determined by flow cytometry. Data shown are one representative experiment of two. Statistical significance was determined using the unpaired t test