Additional critically important lower genes include Wnt regulated master transcription factors TCF7 and LEF1 that are involved in T-regulatory cell differentiation, survival, and immunosuppression (32–34); IL7R connected to T-cell exhaustion and lymphopenia (35); CCR7 implicated in homing and priming of T-cells and antibody response (36); and CD3E connected to combined immunodeficiency (37). The gene discussed is TCF7; the disease is lymphopenia.