Uncovering the ancient roots of immunity, a surprising connection between fever and adaptive immunity has been revealed in a new study on Nile tilapia.
The immune-boosting power of fever has been around for millions of years. In fact, it dates back to a time when our ancestors were still cold-blooded creatures.
Cold-Blooded Creatures and Fever
Fish are the oldest living animals with T cells, which play a crucial role in the adaptive immune system. A new study on Nile tilapia has found that fever triggers the adaptive immune system in these fish. This means that when they get sick, they seek out warmer waters to help fight off infections.
The researchers infected Nile tilapia with the bacterium Edwardsiella piscicida and observed their behavior. The fish preferred to swim in water kept at 34° Celsius, about 5 degrees above their typical temperature. As a result, they had less bacteria in their livers four to six days after infection and more of them survived.
Fever’s Impact on T Cells
Unlike fevers in warm-blooded animals, fish fevers did not cause T cells to multiply into a large number of cells that recognize and attack the specific invader. However, examining fish spleens five days after infection revealed that fever improved T cell survival and ability to kill infected cells.
The researchers found that fever upped T cells’ production of a protein that stops programmed cell death. This effect disappeared eight days after infection, suggesting that disease-fighting T cells were dying off to maintain immune homeostasis.
A Surprisingly Ancient Link
This finding suggests that the link between fever and adaptive immunity arose long ago in animals’ evolutionary history. In fact, it’s believed to date back to a common ancestor of all vertebrates.
“It was really exciting to see a concrete link between fever and adaptive immunity [in fish],” says comparative immunologist Daniel Barreda. “That’s something that hadn’t been solidified before.”
The results show that this is something that had evolved before our ancestors went through the transition from water to land.
A New Perspective on Fever
This study provides new insights into the role of fever in fighting infections. It challenges the common assumption that fevers are simply a symptom of infection. Instead, they play an important role in protecting against infection.
“We might take Tylenol or fever reducers to make us feel better when we have an infection,” says Barreda. “The question is, what are we giving up?
- sciencenews.org | Fever’s link with a key kind of immunity is surprisingly ancient
