Although Mary Poss is still setting up her lab at Penn State's Center for Infectious Disease Dynamics, she takes time to participate in other labs' meetings. A veterinarian and now pathologist, Poss worked on retroviruses before growing frustrated with what she saw as myopia in the research community. She became interested in how viruses leap from one creature to another and how their genes reveal clues about the population dynamics of their hosts.¹ Just a year ago, Peter Hudson, who helped develop the center, invited Poss to come to CIDD. "You want me to come for a seminar?" Poss asked. "No, no," she recalls him saying. "We want you to come." She's already having an impact.

At a recent lab meeting, Hudson's postdoc, Sarah Perkins, was presenting an idea to test how an intestinal worm and a respiratory bacterium, Bordetella bronchiseptica, interact inside the body of a mouse. Such interactions can be important: Julius Wagner von Jaurugg received the 1927 Nobel Prize by showing that the intense fevers of malaria could be used to wipe out syphilis. Perkins suggests that the two parasites may regulate each others' numbers through Th1 and Th2 cytokines, which are thought to interact antagonistically.

courtesy of Mary Poss

Poss takes in the presentation from the back of the room and finally interjects: "I don't know why you're asking about Bordetella and a gastrointestinal parasite."

"Our hypothesis," Perkins responds, "is that an interaction would be immune-mediated." Perkins isn't looking for a direct interaction she says, but an indirect one shaped by the Th1-Th2 tradeoff. From firsthand experience, Poss says, their data would be hard to interpret, and she would be better off looking for signs of an interaction in the field first so they could zero in on a dynamic interaction.

Ultimately, Poss says, the ecologists' ideas about Th1 and Th2 are out of date, as the antagonism occurs on a local scale. "When we're trying to grasp concepts in another field... sometimes we just go to a review paper that makes sense," Poss says. "We're all guilty of that."

"It's just as hard for me to understand the concepts that are very well entrenched in ecology," she adds. In the four months since she arrived, she's already made a convert out of one former Hudsonite - Isabella Cattadori, now a research associate at CIDD. Cattadori and Poss are hunting for antibodies in rabbits.

Perkins, too, says that she'd be meeting with Poss to try to find some middle ground, but she's not ready to pull the plug on the experiment. "I can see it from her viewpoint. But I can see it from mine. She's really got to work to convince me to change my experiment."