Persistence and expansion of donor T cells after GCV-mediated control of GVHD.

Lethally irradiated euthymic [B6 × FVB]F1 (semiallogeneic) or FVB (syngeneic) mice received 1 × 10⁷ FVB BM cells supplemented with 1 × 10⁷ mature T cells from [hCD4 × TK] double-transgenic mice. GCV was administered from day 0 to day 6 (●), whereas controls did not receive GCV (○). At day 7 and day 14 after grafting, splenocytes from grafted animals were collected. CD4 T cells originating from infused TK T cells are unequivocally identified as hCD4⁺ mCD4⁺cells (gated on lymphocytes by size criteria). The lymphoid compartment was analyzed in the spleen at day 7 (end of the GCV regimen) or at day 14. Results are given as mean ± SEM of total cell numbers after gating on the appropriate subsets (semiallogeneic/GCV, day 7, n = 9; semiallogeneic/GCV, day 14, n = 8; semiallogeneic/no GCV, day 7, n = 7; semiallogeneic/no GCV, day 14, n = 4; syngeneic/GCV, days 7-14, n = 4; syngeneic/no GCV, days 7-14, n = 5).