CsA and rapamycin both allow the activation and regulatory action of CD4⁺CD25⁺ T cells. Primary MLR was set up with 1 × 10⁵ responder CD4⁺CD25^- T cells and 5 × 10⁴ γ-irradiated (30 Gy) fully HLA-mismatched stimulator PBMCs. In coculture assays (right), CD4⁺CD25⁺ T cells were added in a suppressor-to-effector ratio of 1:4. CsA and rapamycin were added at the start of primary MLR at indicated concentrations (x axis). Proliferation at day 5 of culture as measured by ³H-thymidine incorporation is shown on the y axis. One representative experiment is shown (n = 5). ^*P < .05 for difference between groups.