The mutation occurs on the gene for CCR-5, a receptor on the surface of macrophages. When a person becomes infected with HIV, the virus latches onto CCR5 and another protein — CD-4 — to be transported inside the macrophages.
CCR-5 is disabled in people with the full mutation, and so HIV is unable to gain access to the macrophages. If an individual inherits the mutant gene from both parents, they are essentially immune to HIV infection. People with one mutant and one normal gene can be infected, but tend to survive longer than infected people with two normal CCR-5 genes. It seems as though people without the mutation, called CCR5-Δ32, were killed by the Black Death, so that those with the mutation survived to reproduce and increase its prevalence today.
就算唔係invincibility 都係increased surviving chance 喎