BTLA functions as a ligand to deliver prosurvival signal in GVHD. (A) Activated BTLA-KO B6 T cells expressing BTLAΔCY-GFP (black bar) or GFP alone (white bar) were transferred intravenously into sublethally (6 Gy)-irradiated BDF1 mice (7 × 105 cells/mouse). After 24 hours, spleen was harvested from the recipient mice and the numbers of GFP-positive donor T cells (total, CD4+, and CD8+) were assessed by flow cytometry. *P < .05. (B) Activated BTLA-KO B6 T cells expressing BTLAΔCY-GFP (black bar), wild-type BTLA-GFP (gray bar), and GFP alone (white bar) were incubated in vitro. After 4 and 7 days, the number of live GFP-positive cells was counted and percentage survival is shown as average plus or minus SD of triplicate wells. *P < .05. (C) T cells isolated from spleen of WT or HVEM-KO mice were labeled with CFSE and stimulated with 2 μg/mL anti-CD3 mAb in the presence of 10 μg/mL immobilized BTLA-Ig or control Ig. After 3 days, the intensity of CFSE of the culture cells was analyzed by flow cytometry. The numbers in panels indicate percentage of cells undergone more than one division.
