Its deletion causes immunodeficiency because of B-lymphocytes produce lower levels of immunoglobulins, tumor necrosis factor (TNF) and lymphotoxin, and because of T-lymphocytes produce lower levels of interferon-gamma (IFNγ) and interleukin-12 (IL-12) promoting differentiation to Th2 phenotype (260, 261). The gene discussed is IFNG; the disease is immune system disorder.