ON THE ADAPTIVE SIGNIFICANCE OF STRESS-INDUCED IMMUNOSUPPRESSION

We approach the field of stress immunology from an ecological point of view and ask: why should a heavy physical workload, for example as a result of a high reproductive effort, compromise immune function? We a rgue that immunosuppression by neuroendocrine mechanisms, such as stre ss hormones, during heavy physical workload is adaptive, and consider two different ultimate explanations of such immunosuppression. First, several authors have suggested that the immune system is suppressed to reallocate resources to other metabolic demands. In our view, this hy pothesis assumes that considerable amounts of energy or nutrients can be saved by suppressing the immune system; however, this assumption re quires further investigation. Second, we suggest an alternative explan ation based on the idea that the immune system is tightly regulated by neuroendocrine mechanisms to avoid hyperactivation and ensuing autoim mune responses. We hypothesize that the risk of autoimmune responses i ncreases during heavy physical workload and that the immune system is suppressed to counteract this.