Effect of TGF-β neutralization on the expansion and proliferation of donor T cells early after SCT. B6 PTPRC^A donors were treated with G-CSF, and purified T cells were labeled with CFSE before transplantation into lethally irradiated allogeneic B6D2F1 or syngeneic C57Bl/6 recipients. (A) Anti-TGF-β or control antibody was injected on days 0 and +1 after transplantation to allogeneic or syngeneic recipients (n = 3 per group), and CFSE intensity was determined in donor (CD45.1⁺) CD4⁺ or CD8⁺ cells 3 days after SCT. (B) The proliferation index (fold expansion of cell population over baseline) of donor CD4⁺ and CD8⁺ T cells was determined by Modfit analysis of CFSE intensity 3 days after SCT. Data are expressed as mean ± SE. ^*P < .05; anti-TGF-β compared with control antibody. □ indicates allogeneic anti-TGFβ Ab; ▪, allogeneic control Ab; ▨, syngeneic anti-TGF-β Ab; and , syngeneic control Ab.