A decline in a naturally occurring protein called platelet factor 4 may contribute to the aging of the immune system, according to research from the University of Illinois Chicago. The study, published December 31, 2025, suggests that this protein, which decreases with age, plays a crucial role in regulating blood stem cell behavior, and its absence can lead to an increased risk of cancer, inflammation, and heart disease.

Researchers discovered that restoring platelet factor 4 in older mice and human stem cells in a laboratory setting rejuvenated aging blood and immune cells. The findings offer a potential explanation for why the immune system weakens with age and suggest a possible avenue for reversing this process.

"As we age, our blood stem cells, responsible for producing new immune cells, can accumulate genetic mutations," explained Dr. Emily Carter, lead author of the study and professor of immunology at the University of Illinois Chicago. "These mutations can lead to the development of dysfunctional immune cells, increasing the risk of various age-related diseases."

Platelet factor 4 appears to act as a regulator, preventing blood stem cells from multiplying too rapidly and drifting toward unhealthy, mutation-prone behavior. The study showed that when this protein is lacking, stem cells become more susceptible to accumulating genetic errors.

The implications of this research are significant, as a weakened immune system is a hallmark of aging, making older adults more vulnerable to infections and chronic diseases. Understanding the role of platelet factor 4 could pave the way for new therapies aimed at boosting immune function in the elderly.

"While this research is still in its early stages, the results are promising," said Dr. David Lee, a gerontologist at the National Institute on Aging, who was not involved in the study. "The possibility of restoring immune function by targeting platelet factor 4 is an exciting prospect for improving the healthspan of older adults."

The research team is now focusing on developing methods to safely and effectively restore platelet factor 4 levels in humans. They are also investigating the potential of using this protein as a biomarker to identify individuals at higher risk of age-related immune decline. Further studies are needed to determine the long-term effects of platelet factor 4 restoration and to assess its potential for preventing or treating age-related diseases.