Whilst we're on the subject of resisting disease, there is a genetic mutation that can render some people virtually immune to HIV. HIV infects the body by entering cells via protein receptors called CD4. Cells with CD4 receptors are an important part of our immune systems and when HIV gets in and destroys them, it compromises immunity causing the HIV to progress to AIDS. It doesn't do this alone, however, as there is another co-receptor called CCR5 that is needed to let it in - you can think of the CD4 receptors as the doors to a fancy hotel and the CCR5 receptors as the guy in the cool hat that opens it for you. The genetic mutation that creates HIV resistance is to this CCR5 receptor and is called CCR5-delta32. With no CCR5 at the door of the cell, the HIV virus is essentially left out in the cold. People with one copy of this mutation have a moderate level of HIV resistance, and the disease is less severe if they do get infected. This level of protection occurs in around 20% of Caucasians. People with two copies of the CCR5-delta32 mutation are basically immune, but this only occurs in around 1% of Caucasians. It's not a good idea to go and get yourself checked for this mutation, however, as it is not a 100% guarantee of never getting HIV/AIDS as the disease itself is also mutating. Better to be safe than sorry.
