Interferon-β (IFN-β) is well known for its antiviral effect, but a new study shows that it may counteract protective immune responses in the context of Mycobacterium leprae infections (Science http://dx.doi.org/10.1126/science.1233665)

Studying IFN responses in human lepromatous lesions, Rosane Teles et al. found an inverse correlation between the gene-expression programs induced by IFN-β and IFN-γ. Healing lepromatous lesions preferentially expressed IFN-γ and its downstream genes, consistent with their known antimicrobial activity. In contrast, disseminated lesions expressed IFN-β and its downstream genes, particularly interleukin-10 (IL-10). Crucially, IFN-β and IL-10 inhibited the IFN-γ–induced antimicrobial response in macrophages in vitro, suggesting that the balance in the production of IFNs may help determine the outcome of infections by M. leprae and perhaps by other pathogens.

The lack of an established animal model of leprosy makes it hard to determine the in vivo relevance of these findings. However, it would be interesting to study whether strategies that block IFN-β and augment IFN-γ–mediated responses promote protection against other mycobacteria.