Pregnancy: success and failure within the Th1/Th2/Th3 paradigm

Evidence from studies on murine and human pregnancy points to a strong association between maternal Th2-type immunity and successful pregnancy on the one hand and between Th1-type immune reactivity and pregnancy loss on the other. While there is a paucity of data from human pregnancy indicating that Th1-type immune effectors actually lead to pregnancy, it is difficult to ignore the compelling evidence linking inappropriate Th1-type immunity to pregnancy loss. Th2-type immunity and TGF beta secreted by Th3 cells may play protective roles during pregnancy, hence the nexus between a Th2/Th3 shift and successful pregnancy. This paper examines these associations and discusses possible mechanisms underlying immunologically mediated pregnancy failure.