Teresa M. Reyes
The chapters of this volume, each in their own way, have addressed the influence of social relations on health. In the previous chapter, Coe and Lubach introduce a discussion of one possible pathway through which social relations could affect health: alterations in immunity. Coe, a developmental psychobiologist, has conducted ground-breaking work in the emerging field of psychoneuroimmunology (PNI). In their chapter, Coe and Lubach describe research done on rhesus monkeys, which has explored the relationship between alterations in the social bond and changes in immunity.
The chapter begins with a brief overview of some early PNI studies in humans, which demonstrated that psychological stress, including such events as bereavement, caregiving for a sick relative, or divorce, resulted in decreased lymphocyte proliferation (one measure of immune function) for one to two months. These types of findings are not restricted to adults but have been found in children as well. Two possible mediators of these immune alterations were considered: glucocorticoids and catecholamines, which are released from activation of two stress-responsive systems, the hypothalamic-pituitary-adrenal (HPA) axis and sympathetic nervous system (SNS), respectively.
Turning to his own research, Coe presents findings on young rhesus monkeys. In these studies, he focused on very early development, from prenatal to neonatal, during which an animal may be particularly sensitive to immune perturbations. When an animal is very young, the immune system, like other physiological systems, is still maturing. Perturbation during this period, even if transient in nature, could change the trajectory of development, which creates a bias for either health or disease. The research examined the immune sequelae after disruption of the social environment, first on older infant monkeys and then moving progressively earlier in development.
The first set of experiments involved a several-day separation of a young animal (6—12 months of age) from either its mother or a peer. Following this stressor, the animals displayed a number of immune alterations, including changes in the number of immune cells in circulation, decreased lymphocyte proliferation, decreased cytolytic activity and decreased antibody response. These findings were consistent and robust, sometimes resulting in decrements up to 50% of baseline. These experiments are a clear demonstration of how acute alterations in social environment can have profound effects on the immune system. However, equally important was the fact that these alterations were transient (usually lasting no more than a week). So it is important to view these findings within the appropriate context. If an animal were challenged by an infection during this one-week period of reduced immunity, it may be at a higher risk for illness. However, it is difficult to hypothesize what a one-week decrease in immune function could mean in terms of overall health, wellness, or longevity. On the other hand, if that