The research is published in the current edition of the Proceedings of the National Academy of Science.

The research focused on an important component of the body's immune system, a certain type of white blood cell called na ve T-cells. These cells are called naive because they have no experience of encountering germs. However, once they encounter germs, they learn and adapt to become strong defenders of the organism. The cells play an important role in the vaccination process because vaccines, which contain either weakened or dead viruses, teach na ve T-cells how to recognize germs and prepare the body for fighting infectious diseases at a later date. Previous research shows that an individual's supply of na ve T-cells diminishes over their lifetime, meaning that in old age a person is more susceptible to infections such as the flu.

Our research identified one actual process by which na ve T-cells are lost later in life, explained Janko Nikolich-Zugich, Ph.D., a senior scientist at the OHSU Vaccine and Gene Therapy Institute and the Oregon National Primate Research Center and a professor of molecular microbiology and immunology in the OHSU School of Medicine.

Throughout our lives, na ve T-cells divide very slowly in our bodies. This helps maintain sufficient numbers of na ve T-cells while we are young. As we age, na ve T-cells are lost and the remaining ones speed up their division to make up for the losses in their numbers. Interestingly, after a certain point, this actually causes the numbers of na ve T-cells to dwindle over time. Our data shows that once the number of na ve T-cells drops below a critical point, the rapidly dividing na ve cells are very short lived. Based on this finding and other information, research suggests that some of the aging Americans may be better protected against disease by finding a way to jumpstart production of new na ve T-cells instead of through revaccination.

Nikolich-Zugich and his colleagues are now working on methods to encourage the body to restart production of na ve T-cells.

Even a slight boost in the number of these important T-cells could protect an aging person against disease for several years, explained Nikolich-Zugich.

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