What is the role of regulatory T cells in the success of implantation and early pregnancy

Problem The immune system is well controlled by the balance between immunostimulation and immunoregulation. CD4+CD25+ regulatory T (Treg) cells and an enzyme called indoleamine-2, 3-dioxygenase (IDO) mediate maternal tolerance of the allogeneic fetus. Treg cells, therefore, may prevent early pregnancy loss due to maternal ‘rejection.’