Tuberculosis is the leading killer of HIV-positive people worldwide, particularly in developing nations, but no one has known for sure exactly why the disease is so prevalent and virulent among HIVers -- until now.
Researchers at Harvard University and the Beth Israel Deaconess Medical Center report in the Journal of Leukocyte Biology that HIV turns off a key immune system response to TB bacterium, both allowing for infection to occur more easily and for TB to become more serious. Specifically, HIV was shown to increase the levels of interleukin-10 in the body, which in turn raised levels of a protein called BCL-3 found in lung macrophages, white blood cells that help the immune system destroy pathogens. When BCL-3 levels are high, the cells lose their ability to fight off TB infection.
"There are still many unknowns about how HIV reduces the ability of the body to combat other infections," John Wherry, Ph.D., deputy editor of the journal, told HIVandHepatitis.com. "This study sheds light on coinfection with HIV and TB, which up to this point has perplexed scientists and physicians alike."