library_construction_protocol: Three biological replicates of sorted CD19+ B cells (naïve, memory, GC DZ, GC LZ, and plasma cells) were isolated and processed for ATAC–seq as described in Buenrostro JD, Wu B, Chang HY, Greenleaf WJ. 2015. ATAC-seq: A Method for Assaying Chromatin Accessibility Genome-Wide. Curr Protoc Mol Biol 109:21 29 1-21 29 9. Samples were run on 2 lanes of the Illumina 4000 HiSeq. ATAC-seq data was processed as previously described.