If indeed an increased incidence of severe TB disease is confirmed among HEU infants, this may be related to increased exposure to TB, or it may further suggest a defect in T cell function or number, and/or defects in interferon gamma (INF-γ) receptor pathways or tumor necrosis factor (TNF) signaling pathways (47, 48), which are necessary for control of mycobacterial infections. Here, IFNG is linked to tuberculosis.