Fetal Immune System Rejects Mother’s Womb, Leading to Preterm Labor

Whenever a woman becomes pregnant, her main concern will always be the safety of her child. However, maintaining a healthy pregnancy can be extremely difficult, especially since many issues are simply out of the mothers control. An unfortunately common issue which many mothers face, is going into preterm labor. Preterm birth occurs when a mother delivers her child prior to 37 weeks of pregnancy, and is considered the number one cause of infant death in the developed world. Despite being such a threat to pregnant women, researchers are unclear what specifically causes a woman to go into preterm labor. A common theory amongst clinicians is that an infection or inflammation may cause the mothers immune system to ramp up and reject her own child. However, a recent publication in Science, has revealed that the truth may be the polar opposite.

In this study carried out by the University of California, San Francisco, researchers collected cord blood from 89 full term babies and 70 babies whose mothers went through preterm labor due to infection. Through thorough analysis of each sample, the results revealed that preterm babies had significantly higher levels of inflammatory cytokines and activated dendritic and memory T cells compared with full term infants. The premature infants cord blood also had a higher prevalence of michrochimerism; the presence of maternal cells in fetal blood, which seemed to stimulate the immune system of premature babies, but not that of full term children. In order to determine if the hyper activated immune system within premature babies had any causative effect on preterm birth, researchers co-cultured the T cells of a premature child with human myometrial cells from the smooth muscle of a uterus. The T cells from premature children seemed to induce contraction of the myometrial cells, where T cells from full term babies had no effect on smooth muscle contraction. From this research, the authors conclude that preterm labor may occur when the mother has an infection which stimulates an inflammatory response, such as TNF-X or IFN-y. This response will inadvertently induce an immune response in the fetus which will eventually lead to contraction of the uterine wall and preterm labor. Now that they have discovered this pathway, the authors are hopeful that they can use this knowledge to help prevent future occurrences of preterm labor, saving children all over the world.

Reference

• Frascoli, Michela, et al. Alloreactive fetal T cells promote uterine contractility in preterm labor via IFN-γ and TNF-α. Science translational medicine 0.438 (2018): eaan2263.