NIAID

The next time you get sick, say a little prayer of thanks for the CD8+ T cell. That's the type of cell whose job it is to kill infected or malignant cells in your body. Your body has many ways of fighting off illnesses, but the CD8+ T cell is one that really kicks your immune system into overdrive.

But in the face of an infection, there often aren't enough of them to do the job, in part because the systems that kick them into gear stop working well. And so your immune system simply gets overloaded by sick cells, a condition known as "immune exhaustion." Now, a group of researchers at Imperial College London has found a new type of protein they say they may be able to kick-start your body's production of CD8+ T cells, which could strengthen your immune system and make your body an infection-fighting machine.

This little cellular super-charger is called the Lymphocyte Expansion Molecule, or LEM for short, a previously unknown protein that helps your immune system grow more CD8+ T cells, according to a new study published this week in the journal Science.

To figure out how they could tweak the activity of CD8+ T cells, the scientists began by genetically screening hundreds of mice. In the process, they found a mutant mouse that produced 10 times as many CD8+ T cells as normal mice. As result, these rodents were better off when they encountered an infection. For instance, eight days after the scientists infected them with lymphocytic choriomeningitis, the viral load in the mutant mice's spleens was 10 million times lower than in normal mice.

The key to these mutant mice's boosted immunity, according to the study, was heightened levels of LEM protein, which in turn produced more active CD8+T cells by supercharging cells' energy production system. These mice also seemed to be more resistant to cancer. When they were injected with melanoma cells, they ended up having one-fourth as many tumors as the normal mice. What's more, the mutant mice also made more memory cells, which act as a sort of biological register of bugs the immune system has seen before. That means that if a previously encountered virus showed up again, they'd be able to fight it off more quickly.

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"Cancer cells have ways to suppress T cell activity, helping them to escape the immune system. Genetically engineering T cells to augment their ability to fight cancer has been a goal for some time and techniques for modifying them already exist," said Philip Ashton-Rickardt, an immunologist from Imperial College London and the lead author of the study, in a statement. "By introducing an active version of the LEM gene into the T cells of cancer patients, we hope we can provide a robust treatment for patients."

Eventually, researchers hope to develop gene therapies that would boost LEM production in normal human cells, giving a much-needed immunity boost to people fighting off cancer and other serious illnesses. Before that can happen, though, they'll need to test whether their approach works safely in mice.

That could be hard. Even though the mutant mice in the study seemed to be better at fighting off infection than the normal mice, they all ended up dying after 14 days, whereas normal mice lived. The researchers say their demise was the result of an adverse effect on the mice's vascular system. Whether that was due to some side effect of the mutation or increased LEM production specifically wasn't clear from the paper.

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Successfully applying these techniques to humans may not happen for several more years. In the meantime, the scientists have filed two patents, and are spinning off a company called ImmunarT to commercialize their technology.

Daniela Hernandez is a senior writer at Fusion. She likes science, robots, pugs, and coffee.