PHILADELPHIA - A team from the University of Pennsylvania School of Medicine and Utrecht University has deciphered a key step in an evolutionarily old branch of the immune response. This system, called complement, comprises a network of proteins that “complement” the work of antibodies in destroying foreign invaders. It serves as a rapid defense mechanism in most species from primitive sponges to humans.

In a study published in the December 24 issue of Science, the groups of John Lambris, PhD, the Dr. Ralph and Sally Weaver Professor of Research Medicine at Penn, and Piet Gros at Utrecht, detail the atomic structure of two key transient enzyme complexes in the human complement system.

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