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Fiona Powrie: Gut diplomacy. Interview by Amy Maxmen.

The immune system's quieter side went unnoticed for some time, while inflammation-inducing proteins soaked up all the attention. Fiona Powrie stepped in just after the concept of inflammation-reducing “suppressor” cells had emerged. In Don Mason's laboratory at the MRC Cellular Immunology Unit in Oxford, Powrie and her colleagues lent the vaguely described cells definition, by showing that one set of CD4+ T cells protected rats from death induced by injecting another set of T cells (1). 
 
 
 
 
 
 
 
 
 
 
Fiona Powrie 
 
 
 
Two decades later, these protective regulatory T cells, now defined by expression of the transcription factor Foxp3, have stolen center stage. And Powrie has been watching them perform one of their most vital tasks: hushing inflammatory responses to food, as well as commensal and other nonthreatening microbes in the gut (2). She helped demonstrate that regulatory T cells in the intestines have the same qualities as those that quell inflammation in response to self-antigens (3). In Bob Coffman's laboratory at the DNAX Research Institute in California, she and her colleagues revealed that regulatory T cells act through the antiinflammatory cytokines interleukin (IL)-10 and transforming growth factor (TGF)-β to counter inflammation driven by tumor necrosis factor (TNF)– and interferon (IFN)-γ–producing effector T cells in mouse models of colitis (4, 5). As chair of the new Translational Gastroenterology Unit at the University of Oxford, Powrie will be working with clinicians to facilitate the application of what she knows about gut homeostasis to patients who've lost it. 
 
“The intestines are really the Wild West of the immune system.” 
 
 
Did your parents influence your decision to become a scientist? 
 
In a way, yes. But not from their own study. My father was in the financial world and my mother was a nurse. But my mother was very ill throughout my childhood with an immune-mediated disease. And that influenced my interest in understanding the immune system and the devastating consequences that problems with that system could have. 
 
Was there a particular moment when you thought, wow, regulatory T cells are cool? 
 
I can remember a time when I was working on my PhD with Don Mason. We were trying to understand the functions of T cell subsets, and we discovered that one subset of T cells led to a fatal disease in the animals and the other subset of T cells inhibited that disease. It was such a striking life-or-death issue that it influenced the rest of my career. 
 
 
 
 
 
 
 
 
 
 
Foxp 3 + (red) and CD4+ (green) regulatory T cells inhabit the spleen. 
 
 
 
Why did you focus on the intestines? 
 
 
The intestines are really the Wild West of the immune system. It's the least understood part and it's in close proximity to a huge number of bacteria. There are actually more foreign cells in your body than your own cells, so the immune system must learn to live peacefully with this beneficial commensal flora. A breakdown of that relationship can cause disease.