CD4 cells are white blood cells that form part of the body's immunity. They protect the body by fighting infection. CD4 count is a blood test which counts the number of these cells. The test shows the stage of HIV infection and results are used to decide what treatment is needed. Treatment (ARVs) is only needed when CD4 count is under 350 and there is high HIV viral load. Your body can contain the HIV virus for a while without you needing ARVs-everyone is different so the time taken before you need ARVs differs person to person.
Attribution: Straight Talk Foundation