In HIV negative people, there are normally between 600 and 1500 CD4 cells per cubic milliliter of blood and 300 to 800 CD8+ cells. The ratio of CD4 to CD8+ cells is two to one. In HIV positive people, CD4 cell counts decline. For HIV positive people not on anti-HIV therapy, it’s common for the CD4 to CD8+ ratio to be reversed. So that’s one thing clinicians evaluate on a lab report—numbers of cells and the ratio of CD4 to CD8+ cells.