CD28 and B-cell chronic lymphocytic leukemia: To further examine how BET-i alleviates CLL-associated T cell exhaustion through chromatin modulation, the assay for transposase-accessible chromatin with high-throughput sequencing (ATAC-Seq) was performed on CD8+ T cells isolated from isolated from CLL patient PBMCs that were treated with 0.5 μM OPN5 or VEH in the presence of anti-CD3/anti-CD28 for 16 hours.