What HIV Does to the Immune System
HIV interferes with the immune response on all levels:
HIV replicates more quickly than the immune system cells and challenges the immune system’s speed and efficacy.
HIV targets CD4+ cells, the cellular managers of the immune system, destroying their ability to activate other immune system cells.
HIV kills the CD4+ cells and puts demands on the body to replace them.
The immune system can replace ten billion CD4+ cells a day. But after years of fending off the virus, it begins to wear down.
The gap between the number of cells killed and the number replaced grows wider over time and eventually leads to AIDS.
Healthy, uninfected people have between 800 and 1200 CD4+ cells per mm of blood.
The number of CD4+ cells declines to dangerously low levels that make a person infected with HIV very vulnerable to the opportunistic infections, cancers, neurological conditions, diarrhea, and weight loss that characterize AIDS.
According to the Centers for Disease Control, a CD4+ cell count below 200/mm is a criterion for AIDS. This also puts the person at high risk for unusual infections.