BTLA expression in the host environment is required for expansion/survival of CD8 T cells.

5×104 purified naïve CD45.1+ WT CD8+ OT-1 cells were adoptively transferred into WT or Btla−/− recipient mice. One day after transfer, mice were orally infected with 1×109 LM-OVA. A- The percentage and absolute number of donor CD45.1+ OT1 cells in the peripheral blood of WT (circles and open bars) and Btla−/− (squares and filled bars) hosts was tracked at different time points following infection. OT1 numbers in the peripheral blood were calculated as indicated in figure 2A. Percentages (B) and absolute numbers (C) of CD45.1+ OT1 cells in WT and Btla−/− recipient mice, 7 days p.i. Data pooled from three independent experiments is shown. D- Percentage and absolute number of memory OT1 cells in the spleen and MLN of WT and Btla−/− recipient mice, 70 days p.i. Data pooled from two independent experiments is shown. E- Co-transfer experiments with WT (CD45.1+CD45.2+) and Btla−/− (CD45.2+) naïve OT1 cells transferred into congenic CD45.1+ WT or Btla−/− recipients. The percentage and absolute number of CD45.2+ WT or Btla−/− cells within total OT1 cells found in the spleen of transferred recipients measured 70 days p.i., is shown. F- Percentage (left) and absolute number (right) of total OT1 cells (CD45.2+) in the spleen, MLN and IEL of co-transferred WT and BTLA-deficient recipient mice, 70 days after LM-OVA infection.