Apoptosis of CD8 T cells in mice infected with H5N1 viruses.

A and B, BALB/c mice were infected with 18 PFU of HK483 or HK486. At the indicated days after infection, the percentages of total CD8 T cells (Panel A) and K^d/NP147-specific CD8 T cells (Panel B) expressing active form of caspase-3 were determined by flow cytometry; cells in the BAL were stained with anti-CD8, K^d/NP147 pentamers, and anti-active caspase-3. Panel C, C57BL/6 (+/+), Fas-deficient (Fas KO) or BIM-deficient (BIM KO) mice (n = 3) were infected with 18 PFU of HK483. On the eighth day after infection, the percentages of total CD8 T cells and of D^b/PA224-specific CD8 T cells expressing active form of caspase-3 in the BAL were determined as in panels A and B above.