X-Linked Lymphoproliferative Disease (XLP) is a rare IEI that is caused by a mutation in the signaling lymphocyte activation molecule (SLAM)-associated protein (SAP) protein-coding gene SH2D1A. Targeted insertion of SAP cDNA at the first exon of the SH2D1A locus was efficiently achieved using TALEN, CRISPR/Cas9, or CRISPR/Cas12a, and SAP protein expression and SAP-dependent immune function were restored in patient-derived T cells (237). This evidence concerns the gene SH2D1A and X-linked lymphoproliferative disease.