HIV enters the body through blood, semen or vaginal fluid. The virus cannot replicate on its own; instead, it seeks out cells so that it can replicate in them as an intracellular parasite. The CD4 T-cell is one of the more common cells that HIV virus particles seek out. A CD4 T-cell is a white blood cell (or lymphocyte). It is an essential part of the immune system that fights against foreign organisms in the body. By entering and replicating in a CD4 T-cell, the HIV virion ultimately destroys that cell. Because HIV replicates quickly and destroys many T-cells, HIV weakens the body’s immune system, making people with the virus more susceptible to additional infections.
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HIV Biology