ADA and severe combined immunodeficiency: Despite the T cell correction and persistence, ADA-SCID results in absence of B and NK cells (in addition to T cells) thus, ultimately HSC-GT has been developed for the condition in order to achieve higher levels of ADA via multi-lineage immune reconstitution (Aiuti et al., 2002; Ferrua and Aiuti, 2017; Kohn et al., 2021).