Homo sapiens Raw sequence reads. Homo sapiens

During pregnancy, the maternal immune system undergoes adaptive modifications necessary for the acceptance and protection of the fetus that would have a long-term impact on maternal health. Conversely, pregnancy complications, such as preeclampsia (PE), will have a negative impact on maternal health. The mechanisms associated with the long-term effect of pregnancy-related immunological modifications are poorly understood. We tested the hypothesis that pregnancy, normal or complicated, establishes a long-term immunological memory that has an impact on consequent pregnancies as well as on maternal well-being. To test this hypothesis, we evaluated the immunological phenotype of circulating immune cells in women 1-2 years after a normal or PE complicated pregnancy. We demonstrate that pregnancy induces long-term changes on specific immune cell subsets and that these changes differ between normal or PE complicated pregnancies. Furthermore, we report that these modifications are due to epigenetic modifications related to the methylation of genes that control T cell and NK cell differentiation and function. We propose the existence of immunological memory of pregnancy (IMOP) as an evolutionary advantage for the success of future pregnancies and the proper adaptation to the microchimeric status established during pregnancy. Our findings demonstrate that the type of immune cell subsets modified during pregnancy may have an impact on subsequent pregnancy and future maternal health.