NOD mice have inherent strain-specific deficiencies in the complement system (Vermaet al., 2017) and thus combinations of these, or other background strain-specific immune gene mutations, combined with susceptibility of the introduced SCID mutation and IL-2Rγ ablation, may culminate in multiple immune-impairments sufficient to allowD. immitis survival and growth. The gene discussed is IL2RG; the disease is severe combined immunodeficiency.