How does HIV damage the immune system and lead to AIDS?

HIV damages the immune system by specifically targeting and destroying helper T cells, also known as CD4+ T cells. These cells are essential to the immune response because they produce factors that activate other critical immune cells, including B cells (which produce antibodies), cytotoxic T cells, and macrophages.123

The virus infects these cells by binding its gp120 protein to the CD4 receptor on the T cell surface, often with the assistance of coreceptors like CCR5 or CXCR4. Once inside, HIV uses the cell's machinery to replicate, eventually causing the death of the host cell. Because the virus replicates rapidly and often mutates, it can evade the body's immune defenses.2

AIDS develops when the rate of helper T cell destruction exceeds the body's ability to produce new ones. As the number of these cells declines, the immune system loses its ability to coordinate an effective defense against infections and pathogens, leaving the body vulnerable to severe disease.21