IFN-γ (type II IFN) is produced by NK cells and macrophages (effector cells in innate immunity), as well as T helper 1 (Th1)-type CD4+ T lymphocytes and CD8+ T cells that participate in the adaptive response [123], being one of the most important and vital pro-inflammatory cytokines for the body’s defense against viral infections [110]. This evidence concerns the gene IFNG and viral infectious disease.