(PHILADELPHIA) -- How do immune cells decide to respond to invading microbes by either fighting to the death or becoming the bodys memory for future infections? Researchers at the University of Pennsylvania School of Medicine have discovered that immune cells can differ in their inheritance of molecules that regulate cell fate, and therefore what role they play in fighting infection. The research appears this week in an early online issue of Science.

"These findings will change the way we look at how vaccines work," says lead author Steven Reiner, MD, Professor of Medicine. "Until now, we have pretty much been in the dark as to how we generate the spectrum of immune cells that are needed to fight off infections. We've always known the end result that more than one type of cell is needed but not the initial events that generate cell diversity. Now we have information that may one day be applied to a more targeted approach to developing vaccines."

Immune cells first need to recognize infecting microbes, then divide and differentiate into the type of immune cells that fight off infection. But how, after replicating, do the new daughter cells know to become fighter cells that are expendable in effect kamikazes and yet reserve some cells to "remember" the invading microbe for future infections?

"That's the conundrum of the immune system and the extraordinary potential of a stem cell," explains Reiner. After the initial infection, some of the descendents of an immune cell reacting to a microbe must become the soldiers that fight the infection and die; but some, instead, regenerate to take the place of the mother cell, leaving an immunologic memory to recognize the invading microbe in the future.

Given the simplicity of this scenario, surprisingly few examples have been well-characterized that show how daughter cells can be different in their inheritance of molecules that regulate cell fate. The Science paper establishes how i
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Contact: Karen Kreeger
karen.kreeger@uphs.upenn.edu
215-349-5658
University of Pennsylvania School of Medicine
1-Mar-2007