IFN-γ in response to any stimuli increased dramatically in grade 2 represented PTB subjects compared to the level of grade 1 which represented heathy control, then slowly went down in grade 3 and slowly went up in grade 4, finally decreased to the very low level which was almost as low as that in healthy control shown in Fig 10, this figure of change trend further demonstrated that IFN-γ depression in PBMC of PTB was associated with cavitary severity of TB, the decreased and very low IFN-γ response will be observed when PTB develops to severe cavities. This evidence concerns the gene IFNG and tuberculosis.