"HIV attaches to a site on our T-cells called the CD4 receptor. T-cells are the soldiers of the immune system that enable us to fight infections. The CD4 receptor is like a window through which HIV enters into body cells. But for efficient entry, HIV attaches to another spot on our T-cells called the CCR5 co-receptor. The CCR5 molecule acts as the most efficient door through which HIV enters into our T-cells. "