Ex vivo expanded and activated CD25⁺ cells inhibit GVHD.

Two million freshly purified naı̈ve B6 CD4⁺ T cells were infused into nonirradiated, NK-depleted BALB/c SCID recipients. Cohorts of mice received a separate injection of 2 × 10⁶activated CD4⁺CD25⁺ cells or CD4⁺CD25⁻ cells. Cells were activated and expanded by immobilized anti-CD3 mAb and high-dose IL-2 for 1 week as described in “Materials and methods.” On the x-axis are days after transfer of cells. On the y-axis is the proportion of recipients surviving (n = 8/group; P = .022 for CD4⁺versus CD4⁺ + Act.CD25⁺).