WEDNESDAY, Nov. 24 (HealthDay News) -- Scientists believe they've discovered how HIV triggers the death of the immune system's defensive CD4 T cells, which in turn leads to AIDS.

It was believed that most immune cells that die in people with HIV are not actually infected, a situation labeled "bystander cell killing." In the new study, the researchers found that these "bystander" cells die because of a failed or abortive HIV infection.

"Our study reveals that the virus actually enters CD4 T cells that are destined to die and that the virus starts to make a DNA copy of its RNA, a process called reverse transcription," lead author Gilad Doitsh at the Gladstone Institute of Virology and Immunology in San Francisco, said in an institute news release.

"However, this process does not work well in the majority of these cells and the incomplete DNA intermediates that accumulate in the [cell's] cytoplasm are sensed and trigger the cells to commit suicide in an attempt to protect the body," he explained.

Doitsh and colleagues also found that the dying CD4 T cells release proteins called cytokines that cause inflammation and attract healthy immune cells, which prompts more infection and immune cell death.

"Our findings have revealed a completely unexpected mechanism for CD4 T-cell death during HIV infection," senior author and institute director Warner C. Greene said in the news release. "These results highlight how a natural cellular defense normally used by the host to repel foreign invaders goes awry in HIV infection, resulting in a profound depletion of CD4 T cells. If untreated, this process ultimately causes AIDS."

The study is published Nov. 24 in the journal Cell.

More information

The U.S. National Institute of Allergy and Infectious Diseases has more about HIV/AIDS.