We transplanted the outgrown cells of starting matched doses (1 × 105) of UCB-derived GE-HSPCs co-cultured with MSCs or standard GE-HSPCs, as control, into sublethally irradiated immunodeficient non-obese diabetic (NOD)-severe combined immunodeficiency (SCID)-IL2Rg−/− (NSG) mice. This evidence concerns the gene IL2RG and immunodeficiency disease.