Pretreatment of recipient mice with FL inhibits donor T-cell activation and expansion to host antigens.

B6D2F1 (CD45.2⁺) mice were pretreated with either 10 μg/d FL or control diluent from day −8 to day −2, followed by 13 Gy TBI and adoptive transfer of T cells from B6Ly5.2 (CD45.1⁺) donor mice. Syngeneic control B6 (CD45.2⁺) mice received B6Ly5.2 (CD45.1⁺) T cells. Spleens were harvested from recipients after transfer of allogeneic T cells in control-treated (dark bar) and FL-treated (hatched bar) animals or transfer of syngeneic T cells (open bar). (A) Number of donor T cells (CD45.1⁺ CD3⁺) was determined by 2-color flow cytometric analysis of splenocytes on day 4. (B, C) Expression of activation markers was determined by the percentage of CD25⁺ (B) and CD49⁺ (C) on donor T cells (CD3⁺ CD45.1⁺) in spleens on day 4. (d) Serum IFN-γ levels were determined in peripheral blood obtained from animals 4 days after adoptive transfer. (A-D) Data represent mean value ± SD of 3 mice. UD indicates undetected.