Importantly for pregnancy, the Th1 cells (in particular IFN-γ) seem to play a role in acute fetal allograft rejection and thus could be involved in recurrent spontaneous abortion (URA) [18,19,20,21,22,23], whereas Th2 cells [20] (producing IL-4 and IL-10) and CD4+CD25+Foxp3+ T reg cells (producing IL-10 and TGF beta), inhibiting IFN-γ production, act to enhance fetal allograft tolerance [24] and thus could be responsible for the success of pregnancy. Here, CD4 is linked to abortion.