Apoptosis is not the major mechanism by which TGF-β and Tsg inhibit responses of human T cells. Primed alloreactive CD4⁺ T-cell lines were cultured with media, anti-CD3 mAb in the presence of either media, TGF-β (2 ng/mL), or Tsg (2 μg/mL) for the indicated time intervals and were subsequently harvested and labeled with annexin V and propidium iodide, and viability was determined by fluorescence-activated cell sorting (FACS) analysis.