Mycobacterium tuberculosis causes an infection that can sometimes kill, but it proceeds to disease in only about 10% of individuals. Now, Montoya et al. provide a clue to how most people keep this bacterium in check. They show that when people fight tuberculosis, their immune cells secrete the cytokine interleukin-32, which may work through an antimicrobial pathway that uses vitamin D. The researchers analyzed five different clinical data sets and found that interleukin-32 may indicate latent tuberculosis. Interleukin-32 therefore may both contribute directly to the host response to tuberculosis and reflect protection against the disease….