Splenocytes were isolated and specific CD8 T cell subsets were sorted by FACS ATAC-seq library was constructed by Nextera DNA Sample Prep Kit (Illumina). For ChIP-seq library, DNA was end-repaired using End-it End-repair kit (Epicentre) and then added an “A” base to the 3’ end of DNA fragments using Klenow (NEB). Then DNA was ligated with adaptors using quick DNA ligase (NEB) at 25°C for 15 min followed by size selection of 200-400 bp using AMPure SPRI beads (Beckman Coulter). The adaptor ligated DNA was amplified using NEBNext High-Fidelity 2X PCR master mix (NEB).