The mystery of how HIV attacks the immune system By Damaris Christensen O ver the past 15 years, governments and institutions have poured millions of dollars into AIDS research. Researchers and doctors have dramatically improved treatments for the disease and gained new understanding of how HIV, the virus that causes AIDS, infects cells. Nevertheless, scientists still understand relatively little about how HIV causes the immune system to collapse, the ultimate consequence of infection. Most researchers have held that HIV directly kills the immune cells called helper T cells, or CD4 cells, eventually exhausting an immune system that is frantically making replacements. The latest studies, however, suggest that different pathways of CD4 cell disruption may be more important.
Some researchers now suspect that the virus chokes off the supply of new immune cells.
Still others are beginning to suggest that HIV changes the signals that send immune cells migrating through the body, directing CD4 cells away from the blood where they normally circulate and toward sites where they may be destroyed. The disagreement is more than an academic issue. Understanding how HIV triggers immune-cell depletion may eventually enable researchers to block its devastating effects. Without knowing more about how HIV ultimately destroys the immune system, however, it is unclear whether drug treatments alone will be enough to restore a person's immune system and perhaps eventually cure the disease. Within 1 to 3 weeks, the immune system gets some control over the virus by producing antibodies and cells that recognize and kill some of the infected cells.