CsA and rapamycin inhibit the allogeneic expansion of CD4⁺CD25⁺ T cells. Freshly isolated CD4⁺CD25⁺ T cells (2.5 × 10⁴) were labeled with CFSE and stimulated with γ-irradiated (30 Gy) HLA-mismatched stimulator PBMCs (1 × 10⁵) in the presence of IL-2 and IL-15. CsA and rapamycin were added at the start of the cultures at indicated concentrations. Cell division represented by the dilution of CFSE was analyzed by flow cytometry at day 6 of culture. Histograms show CFSE intensity (x axis) and the number of events (y axis). One representative experiment is shown (n = 4).