RAG1 and chronic granulomatous disease: This paved the way for the clinical development of HSC-based gene therapy to treat other immunodeficiencies, including the SCIDs X-linked (5–9), Artemis (10–13), RAG1 (14), as well as X-linked chronic granulomatous disease (CGD) (15, 16) and Wiskott–Aldrich Syndrome (WAS) (17–21).