White people are not immune to Sickle cell but, it is said to be a black disease, specifically among racist white supremacist. However, white people are not immune to sickle and they do carry the gene for sickle cell. Watch this video to learn why white people are not immune to sickle cell.
http://www.teenink.com/opinion/current_events_politics/article/155563/Genetics-V-The-Environment-And-Their-Effects-On-Development/
http://www.understandingrace.org/humvar/sickle_01.html
http://www.sahealth.sa.gov.au/wps/wcm/connect/public+content/sa+health+internet/healthy+living/is+your+health+at+risk/the+risks+of+poor+nutrition