ExoHC3
All participants gave written informed consent, who were recruited from Beijing Chest Hospital, a TB specialized hospital in China. The study was approved by the Ethics Committee of Beijing Chest Hospital, Capital Medical University. Patients with active pulmonary TB were diagnosed by significant symptoms of TB with a positive result of T-SPOT.TB test (a commercially available IGRA method), and were further confirmed by Mtb culture of respiratory specimens. The health-care workers without any clinical symptoms suggestive of TB were defined as LTBI according to a positive T-SPOT.TB result. In contrast, the asymptomatic workers who had a  5-year history of close contact to TB patients but persistently showed negative results of both T-SPOT.TB and PPD skin reactivity tests were thought to be resisters. The individuals without known history of exposure to Mtb were included as healthy control subjects based on negative results of both T-SPOT.TB and PPD skin reactivity tests. All participants aged  16 years, and had no significant other medical history such as human immunodeficiency virus (HIV) infection, cancers, and diabetes.