Science
1 May 2009  Vol 324, Issue 5927, Pages 565-663
http://www.sciencemag.org/current.dtl

Origins:
On the Origin of The Immune System
John Travis

Summary
Did the immune system evolve to keep out harmful organisms, or is it like a bouncer at a nightclub, trained to allow the right microbes in and kick the less desirable ones out? In the fifth essay in Science’s series in honor of the Year of Darwin, John Travis explores the evolution of the immune system and how it became the centerpiece of the most dramatic confrontation so far between science educators and scientists determined to keep evolution in the classroom and advocates of the quasi-religious theory known as intelligent design.