TH1/TH2 paradigm in pregnancy: paradigm lost? Cytokines in pregnancy/early abortion: reexamining the TH1/TH2 paradigm.

In this paper, we briefly survey the history of concepts in reproductive immunology from antibody-mediated tolerance to the "fetal allograft" to the current concept of an embryo "bathing in a sea of cytokines". We then review the paradigm that "allopregnancy is a Th2 phenomenon" and some of the evidence gained in animals and humans supporting it. We continue by discussing the light it sheds on immunologically caused recurrent abortion, and the present status of the concepts.

Implantation: can immunological parameters of implantation failure be of interest for pre-eclampsia?

We restate briefly why we consider that the Th1/Th2 paradigm, as useful as it has been, is now no longer adequate and is obsolete. We take as an example the role of IL-18, abortifacient at high doses but cardinal for the control of natural killer (NK) cell effects on spiral artery remodelling in mice, and likely also in humans. We then describe briefly our recent studies on cytokine defects and implantation failure in humans, a key feature being the link between uterine cytokine dysregulation and abnormal uterine vascular scores.