Immune protein may stall HIV. (Immunology).People who don't get AIDS despite harboring the human immunodeficiency virus human immunodeficiency virus n. HIV. Human immunodeficiency virus (HIV) A transmissible retrovirus that causes AIDS in humans. (HIV HIV (Human Immunodeficiency Virus), either of two closely related retroviruses that invade T-helper lymphocytes and are responsible for AIDS. There are two types of HIV: HIV-1 and HIV-2. HIV-1 is responsible for the vast majority of AIDS in the United States. ) for years are more likely than AIDS patients to also have plenty of perforin perforin a protein in cytotoxic T lymphocytes that creates transmembrane pores that act as ion channels in the target cell. Structurally and chemically related to C9 protein of complement which performs a similar function. , a protein that is instrumental in killing infected cells, scientists report in the November Nature Immunology. The AIDS virus AIDS virus n. See HIV. works by hijacking hijacking Crime of seizing possession or control of a vehicle from another by force or threat of force. Although by the late 20th century hijacking most frequently involved the seizure of an airplane and its forcible diversion to destinations chosen by the air pirates, when immune cells called CD4 cells, which disrupts the immune system immune system Cells, cell products, organs, and structures of the body involved in the detection and destruction of foreign invaders, such as bacteria, viruses, and cancer cells. Immunity is based on the system's ability to launch a defense against such invaders. 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. Connors and Stephen A. Migueles led a research team at the institute that examined blood samples from 40 people with HIV, including 15 nonprogressors. Both groups had similar concentrations of CD8 cells. These cells destroy damaged or infected cells by releasing a torrent of chemicals that take apart target cells. Perforin helps the cell-killing compounds gain entry to target cells, Connors says. The CD8 cells of long-term nonprogressors produce more perforin than do CD8 cells of HIV-positive people who developed AIDS, the scientists found. Other evidence indicates that nonprogressors produce CD8 cells that orchestrate attacks specifically against HIV-infected cells. Connors considers these findings "pieces in a puzzle" that he hopes will ultimately reveal an exploitable weakness in the virus that causes AIDS.--N.S. |
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