The host: B and T cells
All blood cells originate in the bone marrow
though T lymphocytes mature in the thymus gland.
T-cells are marked with specific histocapatability molecules in their surface membrane (called clusters of differentiation, or CD) that identify their immune function. All T-cells are marked with CD3, while those marked with CD4 are considered helper-inducer cells, and those marked with CD8 are cytotoxic T-lymphocytes (CTL or killer T-cells) or suppressor cells. NK stands for natural killer cell. CD4+ cells are infected with HIV when HIV binds both to the CD4 molecule and a molecule called fusin. Of course, CD8 cells also get infected with HIV.