Cell suspensions of spleens were prepared and mononuclear cells enriched to >97% human by density gradient centrifugation. The spleen-harvested cells were used for ATAC-seq assay. Buenrostro, J.D., Wu, B., Chang, H.Y. & Greenleaf, W.J. ATAC-seq: A Method for Assaying Chromatin Accessibility Genome-Wide. Curr Protoc Mol Biol 109, 21 29 21-29 (2015).