The Basics: HIV in the Body
The immune system is the body's defense force. It protects the body against infection and disease. HIV is a virus that attacks and weakens the immune system. When the immune system is weakened, the body can't fight infections and diseases, such as TB.
HIV weakens the immune system by hijacking the immune system's CD4 cells. HIV turns these cells into factories to make more copies of HIV. In the process of making more HIV, the CD4 cells are destroyed. This means that as more and more HIV is made, more and more CD4 cells are destroyed. This is why when someone has HIV, and they are not taking ARVS, the amount of HIV in their blood and body goes up (their viral load) as their CD4 count drops.