What is the mechanism of action of TNF-a in tuberculosis?

TNF-α mediates host defense against infection. It is a key player in granuloma formation and containment of M. tuberculosis organisms. TNF-α inhibitors (etanercept, adalimumab, and infliximab) have been associated with reactivation of tuberculosis. Because of this risk, patients must be screened for tuberculosis prior to beginning treatment with a TNF-α inhibitor. If the PPD is positive, but the chest x-ray is negative, the patient may still receive the TNF-α inhibitor after starting antitubercular treatment for latent tuberculosis. The preferred regimen is 6 to 9 months of isoniazid. However, the risk of developing active tuberculosis is not obviated, and there have been reports of this despite an adequate course of isoniazid.

Saraceno R, Chimenti S: How to manage infections in the era of biologics? Dermatol Ther 21(3):180–186, 2008.