Xinxiang Medical University 1 article published in JoVE Immunology and Infection Gene Knock-in by CRISPR/Cas9 and Cell Sorting in Macrophage and T Cell Lines Lichen Zhang1, Rong Huang1, Liaoxun Lu1, Rui Fu1, Guo Guo1, Yanrong Gu1, Zhuangzhuang Liu1, Le He1, Marie Malissen2, Yinming Liang1 1The Laboratory of Genetic Regulators in the Immune System, School of Laboratory Medicine, Xinxiang Medical University, 2Centre d’Immunologie de Marseille-Luminy, Aix Marseille Université This protocol uses fluorescent reporters and cell sorting to simplify knock-in experiments in macrophage and T cell lines. Two plasmids are used for these simplified knock-in experiments, namely a CRISPR/Cas9- and DsRed2-expressing plasmid and a homologous recombination donor plasmid expressing EBFP2, which is permanently integrated at the Rosa26 locus in immune cells.