For ChIP of p300, sorted cells were incubated in fresh media with Flt3L for 2 hours before crosslinking; for ChIP of IRF8, Batf3, H3K27ac, and H3K4me1, cells fixed before purification. Cells were crosslinked with 1% formaldehyde, quenched with 1.25M Glycine, twice washed with PBS. Chromatin was sonicated for shearing DNA size from 140 to 500 bp. Chromatin fragments were immunoprecipitated overnight at 4 °C with Dynabeads Protein A or G bound to anti-p300 (sc-585X, Santa Cruz Biotechnology), anti-IRF-8 (sc-6058x, Santa Cruz Biotechnology), or anti-Batf3, anti-H3K27ac (Ab 4729, Abcam) and H3K4me1 (Ab 8895, Abcam). ChIPed DNA was eluted and reverse-crosslinked for 6 hr. DNA was purified with phenol:chloroform extraction followed by ethanol precipitation. Libraries for ChIP-seq were prepared using ThruPLEX-FD kit (Rubicon Genomics) and sequenced using Illumina HiSeq 2500 as single reads extending 50 bases.