Immunodystrophism: Evidence for a novel alloimmune hypothesis for recurrent pregnancy loss involving Th1-type immunity to trophoblast

Pregnancy loss is the most common complication of pregnancy. Recurrent preg nancy loss occurs in approximately 1% of pregnant women. Many immunologic t heories have been proposed but have not withstood rigorous analysis. A nove l alloimmune hypothesis involving T helper (Th) 1-type immunity to trophobl ast is the latest theory proposed for recurrent pregnancy loss. The basic h ypothesis is, in the decidua there are myriad of antigen presenting cells a nd other immune response cells. In response to trophoblast invasion, these cells may become activated. A by-product of this activation is the secretio n by these cells of either a predominant Th1 or Th2 cytokine profile. In ca ses where a Th1 cytokine profile predominates, chiefly, interferon-gamma, t umor necrosis factor, or interleukin-12, these cytokine may directly or ind irectly be detrimental to early placental cell differentiation and growth a nd toxic to embryo development. Further evidence for this novel hypothesis comes from recent findings of a genetic predisposition for a vigorous Th1 c ytokine response in these women due to a polymorphism in the IL1B promoter region. Further studies are needed to substantiate definitive causative lin ks between Th1-immunity to trophoblast and recurrent pregnancy loss. Clinic al trials are also needed to determine the best therapy for this disorder.