Tuberculosis, caused by the bacterium Mycobacterium tuberculosis (Mtb) kills upwards of 1.6 million people a year, making it one of the leading causes of death by an infectious agent worldwide — and that number is only growing larger. How, exactly, Mtb evades the immune system isn’t yet known, but a collaborative team of researchers recently discovered something surprising: prior exposure to a genus of bacteria called Mycobacterium seems to remodel the first-line defenders in the body’s immune system.