Fasting for three days can regenerate entire immune system, study finds (2014)
telegraph.co.uk
telegraph.co.uk
Here is a paper of one of the researchers quoted: http://cancerres.aacrjournals.org/content/76/14_Supplement/4...
I couldn't find the paper the article was specifically about, but apparently these researchers have been focused on the benefits of fasting for awhile. I would love to see if a meta-study supports their conclusions.