Mice with IL2rg gene disruption have x-linked severe combined immunodeficiency (X-SCID), with the immunodeficiency characterized by a profound loss of T cells, B cells, and NK cells [29,30,31], and IL2RG−/− rats display similar immune cell deficiencies [32]. This evidence concerns the gene IL2RG and T-B+ severe combined immunodeficiency due to gamma chain deficiency.