The R2G2 model is a double knockout mouse with an ultra immunodeficient phenotype. The model was created by backcrossing the IL2RG (common gamma chain) mutation on to a mixed background mouse (C57BL/6 and129 mix) with a mutation in Rag2. The recombination activating gene 2 (Rag2) interruption causes a deficiency in T and B cells. The Common gamma chain gene (IL2RG) interruption results in a lack of functional receptors for IL-2, IL-4, IL-7, IL-9 and IL-15.
Envigo acquired from Fox Chase Cancer Center in 2016, where the model had been maintained since 2005. The model is a white-bellied, light chinchilla (light tan).