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Craig Morrell

Craig Morrell of Molecular and Comparative Pathobiology
on platelets, transplant and malaria:

You went to veterinary school, and then earned your Ph.D. here at Johns Hopkins. Despite the fact that your son thinks you’re a practicing “mouse doctor,” your research niche is platelets. What is it about these tiny tenants of the bloodstream that intrigues you?

MORRELL: If you ask anyone—physicians even—what platelets do, they’re going to say, When you cut yourself, they form a blood clot. But that’s hardly the end of the story. Much less explored and not well understood is how platelets regulate immune response. They’re the second-most numerous cells circulating in the bloodstream (after the oxygen-carrying red variety), so there are tons of them, all jam-packed with potentially active molecules, the roles of which we don’t fully understand. My lab has two main projects related to platelets’ pro-inflammatory qualities: transplant rejection and cerebral malaria.

Malaria is one of the most studied diseases in the world; what do you, a self-described “platelet guy,” bring to the investigation?

MORRELL: I came at it differently from most, not having a background in malaria or public health. My interest is platelets, so I’m applying what we’ve discovered about platelet activation in vascular inflammation to malaria, a model of a vascular inflammatory disease. We’re showing that platelets play an important role in the development of cerebral malaria, through immune- mediated effects.

You also mentioned research related to transplant rejection?

MORRELL: That began with the observation that when transplant tissue is rejected, platelets line up in the interior of blood vessel feeding the tissue. It turns out that they are not just bystanders but have a real role in driving that rejection. In transplant rejection, I think of platelets as the recruiters of immune cells.

Platelets potentially hold sway over all aspects of transplant biology. Our data, as well as others’, show a surprising interplay of platelets and the immune system, so it’s time for the transplant world at large to have platelets on its radar.

What’s next?

MORRELL: Now that we’ve helped establish the fact that platelets regulate immune response by helping to recruit white cells, we want to know how they do that: What are the molecular mechanisms? How are platelets talking to white cells, both locally and systemically, to help drive the process of transplant rejection? One of my goals is to take our basic science knowledge of platelets and apply this to transplantation and transplant rejection. There’s always the impetus toward translational research—to take basic science to the clinicians. You want your work to have some sort of greater impact, but I think perspective is important. What you’ve done may not be used in the clinic in the near future—or ever—but hopefully what you’ve done contributes to someone else’s thinking so it can be pushed in that direction. I think it takes many scientists working on questions to drive these things forward into the clinical setting.