TNF-alpha in tuberculosis: a cytokine with a split personality.

TNF-alpha is an essential component of the innate defence mechanism of the host against pathogenic challenge. Unfortunately, it can also play a major role in the pathology of certain diseases, such as tuberculosis. This disease is a striking example of the role of TNF-alpha as a 'double-edged sword', because apart from its role in controlling the Mycobacterium tuberculosis infection, it can also cause severe tissue damage. TNF-alpha exhibits a very complex network of interactions and many of its activities are still not fully understood. This report aims to review the pivotal role of TNF-alpha in controlling the mycobacterial infection, with a particular emphasis on its influence on chemokine expression and cell movement during granuloma formation, and the issues surrounding the use of TNF-alpha inhibitors for therapeutic use in inflammatory diseases.