Rinku Sengupta, Bee K Tan and Gerard Chaouat
Background: Regulatory T cells (Tregs) are lymphocytes originating in the bone marrow. They mature in the thymus and help fight inflammation in humans. Tregs are involved in the maternal acceptance of the allogeneic fetus. Objectives: This review focuses on the role of Tregs i.e. the origins, development and function in pregnancy, as well as their diagnostic and therapeutic value in pregnancy pathologies such as miscarriage and preeclampsia (PE). Methods: A MeSH and text word PubMed search through August 2016 was performed using the keywords: T receptor lymphocytes; subsets of regulatory T cells: regulatory T cells; controlled trials; pregnancy and treatment. Additional databases searched included; Google scholar, database of abstracts of reviews of effects (DARE), Cochrane Library, NIHR central portfolio management system, UK database of uncertainties about the effects of treatments (DUETs), trip database, health on the NET Northern Ireland (HONNI), the knowledge network Scotland, the Geneva foundation for medical education and research (GFMER) and ClinicalTrials.gov. Findings and conclusions: The origins, development, function and the role of Tregs in the pathophysiology of pregnancy and its complications have not been fully clarified. A lack of Treg cells or defective production due to placental disease or an altered immune response are found in women with sub-fertility, recurrent miscarriage, PE and preterm birth. However, clinical studies to date have involved small numbers of women (with a paucity of randomized controlled trials). Future research focusing on Tregs and their diagnostic and therapeutic value in the management of pregnancy complications are urgently needed.