However, prolonged time to culture conversion observed for IGRA-negative patients (as previously reported by our group) suggests that T cell exhaustion occurring in TB patients leads to reduced control over MTB infection in vivo (14) that, in turn, indicates that recruitment of immune cells by CXCL9 to infection sites cannot overcome deficient IFN-γ-induced activation of macrophages to control the infection. This evidence concerns the gene CXCL9 and infection.