Cell suspensions of spleens were prepared and mononuclear cells enriched to >97% human by density gradient centrifugation. The spleen-harvested cells were used for ChIP-seq assay. Lysates were clarified from sonicated nuclei and crosslinked protein-DNA complexes were isolated with antibody. Library preparation was performed by Novogene (Hong Kong) using a variation of the Illumina's standard protocol. Briefly, the pipeline consists of 3 steps; 1. DNA-end repair, 3'-dA overhang and ligation of methylated sequencing adaptors; 2. PCR amplification and size selection (usually 100-300bp, including adaptor sequence); 3. Qualified library for cluster preparation and sequencing.