Let's look at the structure of the T-cell. T-cells are the main target of HIV in the blood, and act as the host that the virus needs to replicate. (However, macrophages, B-cells, monocytes, and other body cells can also be infected by HIV.) The T-cell has a nucleus that contains genetic material in the form of DNA (deoxyribonucleic acid) (Figure 2). The cell's DNA has all the information that the cell needs to function. The difference between RNA and DNA is that the former is a single strand of genetic material, while the latter is a double strand (Figure 3). This difference is crucial in the process of T-cell infection by HIV.

One important feature in the T-cell's structure is the CD4 receptor site (Figure 2). The CD4 is a protein on the surface of the cells. HIV's gp120 is a mirror image of the CD4. If HIV bumps into the right place on the cell's surface, the gp120 of the virus will lock onto the CD4 site of the T-cell (Figure 4). Because of that, the CD4 is called the receptor site or docking port for HIV

When HIV successfully latches onto a T-cell, the next step will be to inject its core with the viral RNA and the reverse transcriptase.