Question

what cell HIV affects and why that specifically brings down the body's defense system?

why is HIV a crippling disease?

Answer 1

HIV infects and destroys white blood cells in the body's immune system called CD4 cells (or T-helper cells).
At first, virus attaches itself to the CD4 cell and then fuses with it; it destroys CD4 cells by using their replication machinery to produce new copies of the virus, which ultimately results in swelling and bursting of CD4 cells. When the virus has destroyed too many CD4 cells and the CD4 count drops below 200, the body can no longer fight off or defenddefend itself against infections and diseases.

The last stage of HIV infection is AIDS (Acquired immunodeficiency syndrome), which is a chronic, potentially life- threatening condition. At this point, the immune system of the body is too weak to defend against other infections and diseases. When remain untreated, life expectancy is about 3 years with AIDS.