Figure 2

Cultured CD8⁺ T cells suppress naïve T cell proliferation. (a) Dose-dependent suppression of CD4⁺CD25^- responder T cells by cultured CD8⁺ T cells. CFSE-labeled CD4⁺CD25^- naïve T cells (Tn) isolated from B6 spleens were stimulated with anti-CD3 (1.5 μg/ml) in the presence of irradiated splenic APCs with graded numbers of cultured CD8⁺ T cells (Tr). After 72 h in the culture, CFSE dilution in the responder CD4⁺ T cells was analyzed by flow cytometry. T cells in the M2 zone are undivided cells and T cells in the M3 zone with lower CFSE are divided cells. Data are representative of five independent experiments. (b) Naïve CD4⁺CD25^- splenic T cells were cultured in the same condition as shown in (a). The cultures were pulsed with 1 μCi/well [³H]thymidine at 72 h and the level of proliferation was assessed by [³H]thymidine incorporation in the last 16 h of culture. (c) Cultured CD8⁺ T cells (NKT-like), freshly isolated CD4⁺CD25⁺ Treg cells and cultured CD4⁺ cells (cCD4) were compared for their ability to suppress the proliferation of CD4⁺CD25^- responder T cells. Data are presented as percentage of suppression based on the CFSE dilution with standard deviation. ANOVA test suggests that the suppressive ability is significantly different between these cells (p < 10^-6).