Suppressive capacity of CD4+CD25+ cells is decreased more in immunized IFN-γR KO than in wild-type mice. (a, b) Treg cells, Teff cells and accessory cells (ACs) were isolated from lymph nodes and spleen of naive (a) IFN-γR KO and wild-type DBA/1 mice or from IFN-γR KO and wild-type DBA/1 mice 21 days after immunisation with collagen type II in complete Freund's adjuvant (b). In each case, a group of seven to nine mice was used. CD4+CD25- Teff cells (5 × 104) were incubated with anti-CD3 antibody in the presence of ACs and the indicated number of CD4+CD25+ Treg cells. The percentage inhibition (100 × (Radioactivity in condition without Treg cells – Radioactivity in condition with Treg cells)/Radioactivity in condition without Treg cells) of the proliferation of Teff cells (CD4+CD25-) by increasing numbers of CD4+CD25+ Treg cells is shown. Two and seven independent experiments are shown in (a) and (b), respectively. Each result is the mean of two cups. (c) The means of the two (naive mice) or seven (immunised mice) independent experiments shown in (a) and (b). Error bars indicate SEM.