IL2RG and severe combined immunodeficiency: For example, autosomal recessive (AR) complete JAK3 deficiency typically cause severe combined immunodeficiency (SCID) characterized by absence of autologous T and NK cells, highlighting the importance of JAK3 signaling from interleukin (IL)-2 receptor subunit gamma (IL-2RG)-containing IL receptors for development of these lineages (7–10).