For 15 years Marian Cleeves Diamond of the University of California at Berkeley has probed and prodded the brains of rodents in search of some clear connection to the immune system--motivated in part by the memory of her sister, who died more than 50 years ago of an autoimmune disorder. "Someday, I thought, I will find something that correlates with what killed her," Diamond, age 73, said. Now it looks like maybe she has. At the annual meeting of the Society for Neuroscience taking place this week in New Orleans, Diamond reported that women have increased numbers of immune cells after playing contract bridge. Taken together with other studies, Diamond suggests the new results indicate that an area of the brain involved in playing bridge--a part of the frontal lobe--stimulates the immune system, and in particular the thymus gland, which produces T cells. If so, it is the first such cortex-immunity link.

In 1985 Diamond began studying the dorsolateral cortex, a region involved in working memory, planning ahead, initiative and similar tasks. She and her students noticed that in nude mice--immune-compromised animals with deficiencies in their thymus glands--the dorsolateral cortex was thinner than in normal mice. Then in the early 1990s Diamond and her colleagues transplanted normal thymus glands into nude mice only to find that, in addition to restoring their levels of T cells, the new tissue seemed to make the dorsolateral cortex thicken. What they needed next was a way to test the connection in humans. And "contract bridge was ideal for what we were after," Diamond notes, because it demands functions that activate the dorsolateral cortex.

Diamond recruited 12 women in their 70s and 80s from a bridge club in Orinda, Calif., dividing them into three groups for an hour-and-a-half bridge set. Graduate student Jean Weidner drew blood before and after the sets, and in two groups the levels of CD-4-positive T cells rose significantly. Building on her and other researchers' earlier work, Diamond proposes that the dorsolateral cortex mediated this change. "People are aware that voluntary activities like positive thinking and prayer work to keep us healthy, but no one has had a mechanism," Diamond explains. "These data, though preliminary, show that brain activity affects the immune system, and support the possibility of us learning to voluntarily control the level of white blood cells to help combat disease and other illnesses.