A few rare young cells help us fight new diseases better as we age.

A recent study led by Dr. Janko Nikolich-Žugich, head of the UA Department of Immunobiology, found that rare white blood cells, which age more slowly than their counterparts, respond the best to infections as we grow older. Nikolich-Žugich has been tackling questions of aging for 15 years as co-director of the Arizona Center on Aging.

He divides infection-fighting white blood cells, or T cells, into two categories: naïve and memory. Naïve cells fight brand-new infections. They then increase from 100,000-fold up to a million-fold and turn into memory cells. Those are the cells that kick in when your body encounters a strain of flu it already has antibodies against. Memory cells also keep you from getting chicken pox more than once.

Researchers wondered if our aging bodies still called up the same number of naïve cells to respond to new diseases.

After several studies, the answer was no.

“The responses of naïve cells, both in terms of quality and quantity, are never reaching the levels of children and younger adults,” Nikolich-Žugich said. The decline in naïve cells—which shrink to a third of their former levels past age 50 — makes us more susceptible to disease.

The fighting power of kids’ naïve cells against disease is around 90 percent. As we age, it dwindles to between 20 and 50 percent, he said.

But that surviving one-third is the most powerful weapon against fighting disease — and that is what Nikolich-Žugich hopes to capitalize on with the findings of this study. Funded by the National Institutes of Health, it was published in the Proceedings of the National Academy of Sciences.

Nikolich-Žugich said he hopes human trials can start in three to five years on a “kick start” vaccination that would activate and multiply naïve cells. “If we can devise a good vaccination or stimulation protocol, we should be able to selectively expand them even when we grow older,” he said.