In a heroic act of sacrifice, HIV-infected white blood cells known as T cells self-destruct to prevent proliferation of the virus, according to a new study. Unfortunately, their sacrifice is in vain, as the mass die-off of T cells debilitates the body’s immune system, resulting in the immune disorder associated with AIDS. For decades, scientists have puzzled over why this happens, though. Only about 5 percent of T cells become fully infected with HIV, which hijacks the cells’ DNA-replicating system and turns them into factories for pumping out new copies of the virus. So why, then, do the other 95 percent — “bystander” T cells, as they’re known — also fall prey to HIV?

It turns out that these T cells are more like the walking wounded than bystanders, say researchers from the Gladstone Institute of Virology and Immunology in San Francisco, who published their findings this week in the journal Cell.