Of note, IFNγ is important to early life host defense [47] as: 1) low birthweight newborns who are highly susceptible to infection are relatively deficient in IFNγ production[48]; 2) Addition of IFN-γ to human newborn blood in vitro enhanced innate immune function including leukocyte responses to bacteria and plasma opsonophagocytic activity; and 3) IFNγR deficient children present in early life with severe mycobacterial infections[49]. This evidence concerns the gene IFNG and infection.