These fractions are established immuneenhancing components" ("Whey and HIV / AIDS"). In addition, recent research has shown that whey protein has a rich concentration of cysteine, which boosts glutathione (GSH) production. "GSH is an anti-oxidant required for a healthy immune system" ("Benefits of Whey").

The concentration of GSH regulates the body's antioxidant and immune defense system. Other protein sources simply do not have the ability to boost GSH production, as whey protein does. It is this GSH production boost that optimizes many aspects of the immune function. An abundance of cysteine to the liver, through the consumption of whey protein, will boost muscle glutamine production and help maintain immune competence ("Whey and HIV / AIDS").

In the end, proteins are a necessary building block of life. Without protein, the body looks to muscle mass for energy, depleting those stores. Whey protein, specifically, is one of the most bioavailable forms...

This unique protein, a by-product of cheese manufacturing, provides the additional benefit of immune system promotion. The rich concentration of cysteine, in whey protein, boosts GSH production, which is a requirement for a healthy immune system, in addition to other fractions known for their immunoenhancing effects.
References

Benefits of Whey Proteins. 2001. Whey Protein Institute. December 12, 2006 http://www.wheyoflife.org/benefits.cfm.

Oshman, D. & Oshman, P. "Fit & Well: Protein has Big Role in Fitness." Maryland Gazette 8 Dec. 2004: p. C5, ProQuest. ProQuest. University of Phoenix, Phoenix, AZ. December 12, 2006 http://proquest.umi.com.

Whey and HIV / AIDS." Dairy Field 189(1) Jan 2006: p. 48, ProQuest. ProQuest. University of Phoenix, Phoenix, AZ. December 12, 2006 http://proquest.umi.com.

Whey Protein. 26 Nov. 2006. Wikipedia.org. December 12, 2006 http://en.wikipedia.org/wiki/Whey_protein.