T Cells Hunt Like Animals

A surprising new study done by a cross-disciplinary team at the University of Pennsylvania shows that the immune system's T cells use similar hunting strategies to animals found in the wild.

By pairing biology with statistical physics, the researchers found that when hunting parasites, T cells use movement strategies similar to predators such as monkeys, sharks, and even Bluefin tuna. The research could lead to novel approaches when dealing with diseases, and might allow us to better manipulate our T cells to fight infections more efficiently.

It was previously thought that T cells attack in a direct fashion, and that they received the location of parasites and other infections through a complex series of chemical instructions from the rest of the body.

This research, however, shows otherwise.

The T cells observed actually showed no directed motion, and instead had to actively seek out and find the pathogens. In fact, they pause, and examine their surroundings, and are not in constant motion.

"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," said Christopher Hunter, one of the senior authors of the paper and professor and chair of the Pathobiology Department in Penn's School of Veterinary Medicine.

"What that leads to is a much more efficient way of finding things," said  Andrea Liu, the Hepburn Professor of Physics in the Department of Physics and Astronomy.

The researchers studied mice infected with Toxoplasma gondii, a parasite common in both humans and mice. It is estimated that as much as a third of our world population might be carrying T. gondii in a dormant form.

Other diseases such as HIV/AIDS can weaken the immune system, allowing the previously dormant parasite to become an active threat. T cells are known to be a key player in destroying these parasites.

After observing the T cell movements, the pathology team then turned to the physics department for statistical analysis. After wading through various models, the researchers found that the T cell movements fit something known as a Lévy walk, which is simply the key-hunting scenario described above.