THE CONTRIBUTION OF THE IMMUNE-SYSTEM TO PARTURITION

The immune system plays a central role before and during parturition, including the main physiological processes of parturition: uterine con tractions and cervical ripening. The immune system comprises white blo od cells and their secretions. Polymorphonuclear cells and macrophages invade the cervical tissue and release compounds, such as oxygen radi cals and enzymes, which break down the cervical matrix to allow soften ing and dilatation. During this inflammatory process, white blood cell s undergo chemotaxis, adherence to endothelial cells, diapedesis, migr ation and activation. Factors that regulate white blood cell invasion and secretion include cytokines such as tumour necrosis factor and int erleukins. Glucocorticoids, sex hormones and prostaglandins affect cyt okine synthesis. They also modulate the target cells, resulting in alt ered responses to cytokines. On the other hand, the immune system has profound effects on the hormonal system and prostaglandin synthesis. I n animals, nitric oxide has marked effects on uterine quiescence durin g gestation. At the same time, it plays an important role in regulatin g the vascular tone of uterine arteries and has anti-adhesive effects on leukocytes. Cytokines are found in amniotic fluid, and in maternal and foetal serum at term and preterm. Several intrauterine cells have been shown to produce these cytokines. Since neither white blood cells , cytokines nor nitric oxide seem to be the ultimate intermediate for human parturition, the immune system is an additional but obligatory a nd underestimated component in the physiology of delivery. Scientists, obstetricians and anaesthesiologists must thus be aware of these proc esses.