Neutrophils: Diverse functions in the endometrium of cycling women and during pregnancy

This chapter initially provides a brief overview of current knowledge of neutrophil biology, providing background knowledge. It then examines neutrophil contributions to endometrial remodeling during the normal menstrual cycle, menstruation, and subsequent endometrial repair. This is followed by discussion of what is known of neutrophil contributions to placental development, parturition, and maternal immunotolerance. Finally, it examines how disturbances in neutrophil trafficking and phenotype may contribute to disorders such as abnormal uterine bleeding, pre-eclampsia, antiphospholipid syndrome and preterm birth. Importantly, the chapter highlights that while neutrophils predominantly act in concert with other immune cell types as part of the inflammatory cascade, neutrophils also perform specific independent physiological processes within the female reproductive tract. These independent processes are facilitated via release of inflammatory mediators, proteases, extracellular vesicles, and neutrophil traps released into the local tissue microenvironment, which interact with a variety of nonimmune cell types within the local milieu.