Similarly, RIPK1D138N mutation restored numbers of naive CD4+ and naive CD8+ T cells in Tnfaip3.Ikk2ΔTCD4 mice to near normal levels, confirming the dominant role of extrinsic cell death processes in the lymphopenia of Tnfaip3.Ikk2ΔTCD4 mice. The gene discussed is TNFAIP3; the disease is lymphopenia.