Significant discovery holds the promise of a new way to boost immune function in ageing adults

In a world-first, a team from WEHI has made a major discovery in the puzzle that has baffled scientists for decades.

Melbourne scientists may have discovered a secret to the body’s Fountain of Youth.

In a world-first a team from WEHI found a defect in the thymus that could explain why the “tiny but mighty” organ reaches its peak soon after puberty then retires by the age of 65.

Daniel Gray describes it as a significant discovery that holds the promise of a new way to boost immune function in ageing adults.

Professor Gray is a laboratory head at WEHI who led the international team. The results of the team’s study are published in Nature Immunology.

His team uncovered the cells that drive the ageing process in the thymus; an organ that sits behind the breastbone that is important for immunity.

From birth it continues to grow to just under 6cm long, but after puberty it suddenly starts to shrink.

Professor Daniel Gray led the team that uncovered the cells that drive the ageing process. Image: WEHI

“This weakening of the thymus makes it harder for the body to deal with new infections, cancers and regulate immunity as we age,” Professor Gray said.

“This is also why adults who have depleted immune systems, for example due to cancer treatment or stem cell transplants, take much longer than children to recover.”

He says the thymus is the only organ in the body that can make T cells, which are key to the body’s immune defence.

“The thymus is also one of the first organs in the body to begin to decline with age,” Professor Gray said.

Why it stops producing T cells with age has baffled scientists for decades. Until now.

“Using new imaging techniques we were able to, for the first time, peer into the complete thymus structure and discover one of the reasons this happens,” Professor Gray said. “We have uncovered a part of the puzzle.”

The team found scar-like tissue inside the thymus that was compromising its function.

Professor Gray said the reason it atrophies with age, and why it happens so quickly, has been the source of much conjecture.

Reminiscent of a Halloween pumpkin, this collection of dots show cells forming part of the thymus. Image supplied: WEHI

“One of the ideas is you just don’t need it anymore and it’s better to conserve energy,” he says. “Another thought is that thymic atrophy reduces the risk of new immune cells going rogue and causing auto-immune diseases.”

This new study, an international collaboration with groups at the Fred Hutch Cancer Centre in Seattle and the Memorial Sloan Kettering Cancer Centre in New York City, provides crucial and game-changing insights.

“Our discovery provides a new angle for thymic regeneration and immune restoration,” Professor Gray said. “(But) it is not going to stop us from ageing.

Dr Kelin Zhao led the imaging efforts at the WEHI and study lead Professor Daniel Gray. Image: WEHI

“It’s one of the key changes that’s associated with age but where it would really make an impact is in those people at risk following cancer treatment.”

Kelin Zhao led the imaging efforts at the WEHI. She said the findings showed for the first time how the scarring process acts as a barrier to the function of the thymus.

“We’ve proven that changes that occur inside the organ also impact its ability to function with age,” Dr Zhao said.

“By capturing these cell clusters in the act and showing how they contribute to loss of thymic function, we’ve been able to do something no one else has ever done before.”

She says the next steps will be to develop therapies to try to reboot the thymus.

Professor Gray says what the team has achieved is an important discovery.

“We found a unique defect that no one has ever seen before and thanks to the determined efforts of Dr Zhao we built a body of evidence that became really convincing.”

Emeritus Professor Jacques Miller discovered the function of the thymus, revolutionising our understanding of the immune system, infection and disease. Image supplied: WEHI

It is fitting this happened at WEHI. Its Emeritus Professor Jacques Miller discovered the function of the thymus in 1958 which revolutionised the understanding of the immune system, infection and disease.

AT A GLANCE:

• The thymus is an organ that sits behind the breastbone that is important for immunity

• It is essential for good health because it produces T cells that help fight infections and cancer

• The function of the thymus was discovered by WEHI Emeritus Professor Jacques Miller in 1958