Immune Suppression and Th1/Th2 Balance in Pregnancy Revisited: A (Very) Personal Tribute to Tom Wegmann

PROBLEM: The paradigm of local suppression necessary to understand the survival of the fetal allograft is often compared with the host‐tumor relationship. METHODS: We investigated two components of local immune suppression: placenta‐induced immunosuppression, which is mediated at least in part by a soluble factor of low molecular weight that can induce anergy in lymphocytes, and interleukin‐10 (IL‐10). RESULTS: We show that enhancement of IL‐10 production in the decidua and placenta after alloimmunization requires the presence of Asialo GM1+ cells. Placenta‐induced immunosuppression is linked with defects in phosphorylation of some components of the T cell receptor. CONCLUSION: NK cells could be in fact regulatory cells pushing maternal immune response toward a Th2 profile, beneficial for fetal survival, or toward a Th1 type of immune response, which acts in synergy. Modulation of TcR may represent a new mechanism for maternal‐fetal tolerance.