HVEM promotes the survival of OT1 cells after LM-OVA infection.

Purified naïve WT or Hvem−/− CD8+ OT1 cells were adoptively transferred into CD45.1+ recipient mice and one day later, mice were orally infected with LM-OVA. A- HVEM expression on naïve OT1 cells and OT1 cells isolated from peripheral blood of LM-OVA infected mice was assessed at the indicated times after infection. To analyze the early expansion of WT and Hvem−/− CD8+ T cells in mice infected with LM-OVA, 5×105 CFSE-labeled WT or Hvem−/− OT1 cells were transferred into CD45.1+ recipients and the percentage of OVA-specific T cells in the MLN of the hosts, 4 days p.i., was analyzed (B). Proliferation of WT and Hvem−/− OT1 cells in the MLN of infected mice was assessed by CFSE dilution profiles (C). Histogram shows the percentage of WT (open bar) and Hvem−/− (filled bar) OT1 cells undergoing more than two cell divisions. The accumulation of activated CD8+ effector T cells was also monitored at day 5 p.i., by measuring the percentage and absolute number of WT and Hvem−/− OT1 cells in the spleen and MLN of LM-OVA-infected animals (D). The ability of WT and Hvem−/− OT1 cells to expand and contract following LM-OVA infection was determined by tracking the percentage and absolute number of the CD45.2+ OT1 cells in the spleen of infected mice at different time points after infection (E). The proliferation of WT and Hvem−/− OT1 cells in the spleen of infected mice at the peak of the immune response was evaluated by measuring the intracellular levels of the proliferation marker Ki-67 (F).