For example, several immunodeficient rabbit lines have been produced by knocking out of genes such as Il2rg, Foxn1, and Rag2 (Song et al., 2013, 2017; Yan et al., 2014; Hashikawa et al., 2020); these animals are expected to make valuable contributions to regenerative medicine, cancer and primary immunodeficiency, as comprehensively reviewed elsewhere (Song et al., 2020). The gene discussed is RAG2; the disease is cancer.