People who don't get AIDS despite harboring the human immunodeficiency virus (HIV) for years are more likely than AIDS patients to also have plenty of perforin, a protein that is instrumental in killing infected cells, scientists report in the November Nature Immunology.
The AIDS virus works by hijacking immune cells called CD4 cells, which disrupts the immune system in most people. Other cells of the immune system, CD8 cells, usually fail to defend against the virus.
But in a small group of HIV-infected people known as long-term nonprogressors, those CD8 cells seem to stave off the development of AIDS, even in the absence of anti-HIV drugs. The difference may be the quality of the CD8 cells, not the quantity, says study coauthor Mark Connors of the National Institute of Allergy and Infectious Diseases in Bethesda, Md.