Here is a short article that talks about the importance of glutathione:

http://www.dfwcfids.org/medical/whey.html

By the way, in addition to the expensive Immunocal, ImuPlus, or ImmunePro, the Fat Flush Whey Protein Powder claims to be undenatured as well - it only costs somewhat more than normal whey protein powder for bodybuilding etc.