Generation and characterization of RAG2 knockout pigs as animal model for severe combined immunodeficiency

Pigs with severe combined immunodeficiency (SCID) are versatile animal models for human medical research because of their biological similarities to humans, suitable body size, and longevity for practical research. SCID pigs with defined mutation(s) can be an invaluable tool for research on porcine immunity. In this study, we produced RAG2-knockout pigs via somatic cell nuclear transfer and analyzed their phenotype. The V(D)J recombination processes were confirmed as being inactivated. They consistently lacked mature T and B cells but had substantial numbers of cells considered to be T- or B-cell progenitors as well as NK cells. They also lacked thymic medulla and lymphoid aggregations in the spleen, mesenteric lymph nodes, and ileal Peyer's patches. We showed more severe immunological defects in the RAG2 and IL2RG double-knockout pig through this study. Thus, SCID pigs could be promising animal models not only for translational medical research but also for immunological studies of pigs themselves.