TNF and tuberculosis: Although it was not significantly different in response to ESAT-6 between TB patients and contacts, TNF-α production in response to ESAT-6 was higher in the S2 spouses compared with TB patients, suggesting that the level of TNF-α in response to ESAT-6 and PPD might be an additional marker for LTBI to help differentiate them from TB patients as well as uninfected controls.