How does HIV Infect a Cell?
For many years it has been known that HIV infection primarily occurs when HIV binds specifically to a protein in the cellular membrane of lymphocytes called T-helper cells (although, very recent information now shows other important requirements for cellular entrance – see below – additional information – last paragraph). These cells express and are identifiable by this expression of a protein within their cellular membrane called CD4 (Cluster of Differentiation antigen number 4). Normally, this particular T-helper cell membrane-associated protein is required for the ability of the T-helper cell to participate effectively in an immune response (to help other important lymphocytes express _their_ activity, e.g., B-lymphocytes and antibody production, and cytotoxic T-cells’ ability to kill virally infected cells). Therefore, HIV infects the very cell required to help other immune system cells to protect us from any foreign thing which enters our body. What Happens When HIV Enters the Cel
