An immune clock of human pregnancy

High-dimensional analysis reveals the chronology of immunological adaptations during the course of human pregnancies. Following the hand of the immunological clock Immune function is altered during pregnancy to protect the fetus from an immunological attack without disrupting protection against infection. Now, Aghaeepour et al. use mass cytometry to examine the precise timing of these pregnancy-induced changes in immune function and regulation. They developed an algorithm that captures the immunological timeline during pregnancy that both validates previous findings and sheds new light on immune cell interaction during gestation. By defining this immunological chronology during normal term pregnancy, they can now begin to determine which alterations associate with pregnancy-related pathologies. The maintenance of pregnancy relies on finely tuned immune adaptations. We demonstrate that these adaptations are precisely timed, reflecting an immune clock of pregnancy in women delivering at term. Using mass cytometry, the abundance and functional responses of all major immune cell subsets were quantified in serial blood samples collected throughout pregnancy. Cell signaling–based Elastic Net, a regularized regression method adapted from the elastic net algorithm, was developed to infer and prospectively validate a predictive model of interrelated immune events that accurately captures the chronology of pregnancy. Model components highlighted existing knowledge and revealed previously unreported biology, including a critical role for the interleukin-2–dependent STAT5ab signaling pathway in modulating T cell function during pregnancy. These findings unravel the precise timing of immunological events occurring during a term pregnancy and provide the analytical framework to identify immunological deviations implicated in pregnancy-related pathologies.