Above is a popular scanning electrom micrograph of numerous HIV-1 virions (green) emerging from a cultured white blood cell. HIV has caused millions of deaths since the early 80s, but some individuals are actually immune to contracting the strain of the virus depicted above. Note: This isn’t a recommendation for risky behavior to see if you’re immune; HIV/AIDS is devastating and incurable.
The HIV-1 virus operates by detecting a protein on the surface of T-lymphocytes called CCR5. In some individuals, a 32 base pair deletion in the gene leads to defective CCR5 proteins that are absent from the white blood cell surfaces. If there is no CCR5 protein to bind to, the HIV virus cannot begin its attack on the immune system. Thus, these individuals will be resistant to HIV-1.
Image Source: http://phil.cdc.gov/phil/details.asp?pid=10000