Insufficient IL-17 increases (sequentially) HIF-1α expression, hypoxic necrotic granuloma formation, & severity of TB (87). IL-17 also required for initial formation of protective iBALT (89, 90, 119). IL-17 triggers the production of chemokines that recruit CD4+IFNγ+ T cells (88). This evidence concerns the gene CD4 and tuberculosis.