Figure 2.

Effect of CD4⁺ regulatory T cells (T_regs) and regulatory B cells (B_regs) on T cell function in vitro. (a) Wild‐type (WT) and B7‐2^–/– T_regs suppressed T cell proliferation with similar efficacy in vitro. CD4⁺CD25⁺ T_regs from 3‐month‐old female mice were co‐cultured with CD4⁺CD25^– T cells from spontaneous autoimmune polyneuropathy (SAP) mice (8 months) in the presence of 20 μg/ml P0 (180–189) and irradiated antigen‐presenting cells (APCs) (50 000) for 3 days. Proliferation was measured by [³H]‐thymidine incorporation (n = 3). (b) WT and B7‐2^–/– B_regs (CD19⁺CD1d^hi CD5⁺) did not suppress the proliferation of CD4⁺CD25^– T cells at a 1 : 1 ratio (n = 3). (c) WT and B7‐2^–/– T_regs had no effect on CD4⁺interferon (IFN)‐γ or CD4⁺interleukin (IL)−17⁺ cells, but increased the percentage of CD4⁺IL‐10⁺ T cells in co‐cultures. Experimental conditions were the same as in (a), except that T_regs were obtained from WT or B7‐2^–/– NOD mice killed at 10 days post‐immunization with P0 (180–199). T_reg : CD4 ratio was 1 : 1. *P < 0·02; **P < 0·0005 (n = 3). (d) WT and B7‐2^–/– B_regs induced a decrease in CD4⁺IFN‐γ⁺ T cells and increase in CD4⁺IL‐10⁺ T cells in co‐cultures. B_regs sorted from immunized animals were co‐cultured with CD4⁺CD25^– T cells at a  : 1 ratio for 3 days in the presence of P0 (180–199), lipopolysaccharide (LPS) (100 ng/ml) and irradiated antigen‐presenting cells (APCs) (50 000). *P < 0·002; **P < 0·0001 (n = 3).