The consequences for human reproduction of a robust inflammatory response

Innate and adaptive immune responsiveness is variable within the population. Since robust immune reactions are critical to the survival of humans, the existence of immune variability in the population suggests the existence of competing, alternative phenotypes. Although women with powerful immune responsiveness may be more likely to survive to reproduce, their reproductive experiences may be less successful than women who are not as responsive. Normal pregnancy elicits a maternal inflammatory reaction. This can be understood on the basis of maternal-fetal conflict theory: inflammation is a component of the maternal attempt to limit excessive fetal demands. However, an overly aggressive inflammatory reaction has been shown to relate to a variety of adverse reproductive outcomes. Reviewed here are several examples, including the fallopian tube damage that results from pelvic inflammatory disease, the upregulated inflammatory response among women who develop preeclampsia, an association between immune hyperresponsiveness and premature delivery, and the relationship between autoimmune diseases and multiple adverse pregnancy outcomes. The hypothesis that immune hyperresponsiveness limits reproductive capacity suggests many avenues for research.