The SD-Rag2 KO rat is an immunodeficient model with the Rag2 gene knocked out, and it can be used for extensive research in oncology and immunology. Studies have shown that the absence of functional RAG2 protein can lead to severe combined immunodeficiency (SCID). The deletion of the Rag2 gene in rats results in the absence of V(D)J recombination, blocking the differentiation, development, and maturation of T cells and B cells. This manifests as severe thymic hypoplasia, with no mature T and B cells, but a compensatory increase in NK cells.