A protein called platelet factor 4 (PF4) naturally declines with age, potentially explaining why the immune system loses its effectiveness over time, according to research from the University of Illinois Chicago. The study, published December 31, 2025, found that this decline allows blood stem cells to multiply excessively, leading to mutation-prone behavior associated with cancer, inflammation, and heart disease.

Researchers discovered that restoring PF4 in older mice and human stem cells in a laboratory setting rejuvenated aging blood and immune cells. The findings suggest a potential pathway for reversing age-related immune decline.

"As we age, the stem cells responsible for producing blood and immune cells can accumulate genetic mutations," explained Dr. [Lead Researcher's Name], lead author of the study and professor at the University of Illinois Chicago. "This accumulation increases the risk of various health problems, including cancer."

The immune system's decline with age, known as immunosenescence, is a significant factor in the increased susceptibility to infections and autoimmune diseases in older adults. This study sheds light on a previously unknown mechanism contributing to this decline.

Platelet factor 4 is a small protein released by platelets, which are blood cells involved in clotting. It plays a role in regulating blood cell production and inflammation. The study revealed that PF4 acts as a brake on blood stem cell proliferation, preventing them from dividing too rapidly and accumulating mutations.

"We observed that as PF4 levels decrease, blood stem cells become more prone to uncontrolled division," said [Co-author's Name], a researcher involved in the study. "This leads to an increase in cells with mutations, which can ultimately contribute to the development of age-related diseases."

The researchers conducted experiments on both mice and human cells. In older mice, restoring PF4 levels improved the function of their immune cells and reduced the number of mutated blood stem cells. Similarly, in human stem cells grown in the lab, adding PF4 reversed some of the signs of aging.

While the findings are promising, experts caution that more research is needed before these results can be translated into clinical applications. "This is an exciting discovery, but it's important to remember that we are still in the early stages of understanding the role of PF4 in aging," said Dr. [External Expert's Name], an immunologist at [Other Institution], who was not involved in the study. "Further research is needed to determine the optimal way to restore PF4 levels in humans and to assess the potential risks and benefits of this approach."

The research team is now focusing on developing strategies to safely and effectively increase PF4 levels in older adults. They are also investigating the potential of PF4 as a therapeutic target for age-related diseases. The study offers a new perspective on the aging process and highlights the potential for interventions that target specific proteins to improve immune function and overall health in older individuals.