DST does not tolerize Th cells to donor alloantigen. Spleen and LN cells were prepared from untreated naive or DST-treated (1 mL on days −14 and −7) rats 14 days after the first transfusion. Cells (2 × 10⁵) were plated in triplicate with an equal number of donor-specific Lew.1W (RT1.u) (A) or third-party Buffalo (RT1.b) (B) irradiated spleen cells in 96-well round-bottom plates and cultured for 1 to 7 days. Thymidine incorporation during the last 8 hours of each of these cultures was assessed. Representative data of three independent experiments are shown.