Photodepletion (PD) cells display reduced proliferation and mostly a Treg phenotype. (A) PBMCs from chronic GVHD patients (n = 10) were exposed (or not) to photodepletion. Proliferation of GVHD cells was assessed by ³H-thymidine incorporation after 5-day cultures in the presence of IL-2. (B) Three days after photodepletion, CD4⁺CD25⁺ cells were evaluated by flow cytometry and activated, and Treg cells were discriminated by FOXP3 expression. Shown are representative examples and a compilation of 6 independent experiments ± SD expressed in relative (C) and absolute (D) number. Clear bars and filled bars represent untreated (untx) and photodepletion-treated GVHD PBMCs, respectively. **P < .01 and ***P < .001