Hunter likened the model to a strategy a person might employ to find misplaced keys in the house.
"When you lose your keys, how do you go about looking for them? You look in one place for a while, then move to another place and look there," he said.
"What that leads to is a much more efficient way of finding things," Liu said.
And, indeed, when the team modeled the generalized Lvy strategy against other strategies, they confirmed that the Lvy walk was a more efficient technique to find rare targets. That makes sense for T cells, which have to locate sparsely distributed parasites in a sea of mostly normal tissue.
Interestingly, T cells are not alone in employing a Lvy-type strategy to find their targets. Several animal predators move in a similar way with many short-distance movements interspersed with occasional longer-distance moves to find their prey. The strategy seems particularly common among marine predators, including tuna, sharks, zooplankton, sea turtles and penguins, though terrestrial species like spider monkeys and honeybees may use the same approach to locate rare resources.
This parallel with animal predators also makes sense because parasites, like prey species, have evolved to evade detection.
"Many pathogens know how to hide, so T cells are not able to move directly to their target," Hunter said. "The T cell actually needs to go into an area and then see if there's anything there."
The model is also relevant to cancer and other immune-mediated diseases, Hunter noted.
"Instead of looking for a parasite, these T cells could be looking for a cancer cell," he said. By knowing what controls T cell movement, "you might be able to devise strategies to make the T cells more efficient at finding those cells."
On the physics side, while the Lvy-walk model is not new, the fact that T cells pause in between their steps or runs
|Contact: Katherine Unger Baillie|
University of Pennsylvania