STRESS: big problem for natural born killers Life's stressful events really do get under our skin. In fact they seem to reach all the way to the immune system, and weaken our ability to battle illness.

PNI (or psycho- neuroimmu- nology) diagram illustrates how psychological events can influence immune responses. Source: Christopher Coe, University of Wisconsin-Madison psychologist.

The body's battalion of natural killer white blood cells are relentless terminators on a seek-and-destroy mission against microbial intruders and damaged cells. But University of Wisconsin-Madison psychologist Christopher Coe has found that both the number of these cells and their performance decline when stress puts the brain on red alert. In the kind of test only a professor could love, Coe evaluated students in the throes of final exam week. After screening students for their pre-existing emotional states and quality of relationships, Coe then took blood samples before and during finals. Then he separated the killer cells and mixed them with cancer cells to determine their ability to kill the tumor cells. He consistently found that exam-time stress reduced the natural ability to lyse -- to punch a hole -- in the cancer cell. In studies with UW-Madison colleague Richard Davidson, the size of the decrease in the immune system could be predicted by brain electrical patterns that correlated with the students' emotional state -- whether they were happy, lonely or depressed. The same appears to be true for people who are predisposed to negative thoughts and emotions. In other words, if you're a pessimistic, "glass-is-half-empty" type, your immune system could also be running on empty. Another study looked at Madison-area high school students with asthma. Working with nursing researchers Duck-Hee Kang and Donna McCarthy, Coe wanted to see how the stress of finals affected the amount of superoxides (a type of free radical that can injure cells) produced by a type of white blood cells called the neutrophil. An over-production of superoxides could aggravate the inflammation and irritability of the lungs in asthmatics. Coe found that the stress also affected the neutrophil cells. In this case, the students' inflammatory response increased dramatically during exams, and stayed up even two weeks after the exams. The silver lining in this study, however, was that students with well-managed asthma who regularly used their inhalers did not have problems with lung function. Do finals cause cancer? So we can conclude that finals should be eliminated because they're a health hazard, right? Professor Coe says that overstates the case. "I don't want to argue that taking exams causes cancer," he says. "For most of us, it really will not matter if some of our immune responses go down or up. We will still stay healthy. But the same type of immune changes may have greater consequences at other points in the life span, such as in young children and in old age." That's really the take-home message in Coe's research. Before puberty, the immune system is in a formative stage, and stressful events can alter its natural course. Think of it this way: If you pushed a guided missile slightly off-course, its wayward path might not show up until it missed its target. Similarly, these early immune problems might cause trouble at old age, when we go through immune "senescence" -- a natural "going to sleep" of the immune system. Got them separation blues? Studies with rhesus monkeys showed large responses to stress, when, for example, infants were taken from their mothers at six months of age. The young monkey's immune cells didn't grow as well, didn't function properly, and produced fewer antibodies. Furthermore, babies from pregnant rhesus monkeys who were exposed to a minor stress for just 10 minutes a day for six weeks had altered immune systems. Despite this hard data, Coe says scientists can't yet draw a red line on the stress meter, saying this much and no more. But it's easy to imagine that terrible living conditions -- witness the turmoil of Rwanda and Zaire -- could take a toll on children and may be causing lasting damage to their immune systems. In collaboration with psychologists Megan Gunnar and Mary Carlson, Coe is completing a study of children in Romania's horribly understaffed orphanages. In samples of saliva, the researcher found troubling evidence of disease exposure and compromised immunity. The Romanian children were producing excessive antibodies to the bacteria that causes meningitis and the common cold-sore virus, suggesting their bodies were unable to control these microbes. (American children usually have no sign of these antibodies.) The lesson here, Coe says, is that preventing emotional turmoil may be a kind of preventive medicine. "You can empower people to alter their perceptions," he says, "and thereby to prevent these immune changes from occurring." If you want to alter your perceptions, check out our bibliography!

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