Alkaline compound helps the tuberculosis bacterium to ward off an acid attack from host cells.

The bacterium that causes tuberculosis has devised an effective form of self-defence: it neutralizes immune cells with antacid.

Mycobacterium tuberculosis, the world’s leading infectious killer, can dwell in a person’s body for years by hiding in immune cells that swallow pathogens. These cells usually destroy dangerous microbes in acidic compartments known as phagolysosomes, but M. tuberculosis often evades this fate.

A team led by Branch Moody at Brigham and Women’s Hospital in Boston, Massachusetts, reports that M. tuberculosis strains infecting people tend to produce massive quantities of a molecule that acts as an antacid. The molecule, named 1-tuberculosinyladenosine (1-TbAd), neutralizes the otherwise acidic environment inside phagolysosomes.