CD8+ effector T cells were sort-purified on day 4 post-infection, the cells were then fixed and sonicated to generate chromatin fragments, followed by immunoprecipitation with antibodies against H3K4Me1, H3K4me3, H3K27me3, or H3K27Ac, which were then properly washed and immunoprecipitated DNA extracted. For ChIP-Seq of CBF, naive CD8 T cells and CD8+ effector T cells (sorted on day 8 post-infection) were isolated and immunoprecipated with an anti-CBF antiserum. The DNA segments from ChIP were end-repaired and ligated to indexed Illumina adaptors, followed by amplification by PCR with a low number of cells (18-21 cycles). The resulting libraries were seqeunced with Illumina Hiseq-2000 platform.