The RAG2 gene encodes a protein that, together with the RAG1 protein, forms the RAG complex, playing a crucial role in V(D)J recombination during the maturation of B and T cells. During V(D)J recombination, the RAG complex attaches to the recombination signal sequences (RSS) located adjacent to V, D, or J segments in the DNA. The RAG complex cuts the DNA between the signal sequences and the segments, allowing the segments to separate and move to different regions of the genome. This process occurs repeatedly in B and T cells, arranging the V, D, and J segments in various combinations. The resulting protein diversity provides a broader capability to recognize foreign invaders, allowing the body to combat infections effectively. RAG2 is essential in V(D)J recombination, not only catalyzing the reaction but also regulating it by controlling access to specific loci. A lack of functional RAG2 protein can also lead to severe combined immunodeficiency (SCID). In mice, deleting the Rag2 gene results in the absence of V(D)J recombination, blocking the differentiation, development, and maturation of T and B cells, which lose their normal functions, leading to a SCID-like phenotype.

Rag2 KO mice are Rag2 gene knockout (KO) models. Homozygous Rag2 KO mice develop normally and are fertile but do not produce mature T and B cells. They can be used in research on immune system deficiencies, cancer, toxicology, and xenotransplantation.