Cd11b+ cells were isolated using Magnetic activated cell sorting (MACS) and cryopreserved with 5% DMSO to allow slow cooling rate inorder to minimise cell lysis. Further, viable cells were prepared for library using the original procedure (Buenrostro et al., 2013) with some added modifications for frozen cells (Fujiwara et al., 2019).Briefly, cell pellets were re-suspended in ice-cold lysis buffer (10 mM Tris-Cl, pH 7.4, 10 mM NaCl, 3 mM MgCl2, and 0.1 % (v/v) Igepal CA-630) to extract the cell nuclei The library of transposed DNA fragments was prepared according to  (Buenrostro et al., 2013).DNA was purified with the ZymoResearch DNA Clear & Concentrator TM-5 kit and eluted in 10 µl of elution buffer. qPCR was then performed to determine the additional number of PCR cycles required for the final library. The profiles of libraries were assessed with the Bioanalyzer2100.