Scientists have discovered that HIV does not cause AIDS by the virus's direct effect on the host's immune cells, but rather through the cells' lethal influence on one another. In a new study, the researchers revealed that the HIV 'death pathway' -- how 95 percent of cells die from the virus -- is only initiated if the virus is passed from cell-to-cell, not if cells are infected by free-floating viral particles.

Source: HIV particles do not cause AIDS, our own immune cells do