Tolerating pregnancy

The activity of specific suppressive immune cells, some of which persist to aid subsequent pregnancies, helps to explain how a pregnant female's immune system tolerates fetal antigens inherited from the father. See Letter p.102 Immune defence of the fetus Successful pregnancy requires the development of effective tolerance mechanisms for fetus antigens inherited from the father, which evoke an immune response because they are considered ‘non-self’ by the maternal immune system. Jared Rowe et al . show here that this is accomplished by the generation of maternal regulatory T cells with specificity for fetal antigens. Fetal-specific regulatory T cells re-accumulate with accelerated kinetics during secondary pregnancy and may explain why partner-specific secondary pregnancies show reduced rates of pre-eclampsia and other complications.