%0 Journal Article
%T The Role of PPARs in Placental Immunology: A Systematic Review of the Literature
%A Stefan Hutter
%A Julia Knabl
%A Ulrich Andergassen
%A Udo Jeschke
%J PPAR Research
%D 2013
%I Hindawi Publishing Corporation
%R 10.1155/2013/970276
%X Pregnancy is a state of immunotolerance, and pregnancy outcome is strongly linked to the correct activation and balancing of the maternal immune system. Besides abortion as possible result of improper early pregnancy development, other pregnancy associated conditions like preeclampsia (PE), intrauterine growth retardation (IUGR), preterm labour, or gestational diabetes mellitus (GDM) are linked to immunologic overactivation and dysregulation. Both the innate and the adaptive immune system, and therefore B and T lymphocytes, natural killer cells (NK), macrophages and dendritic cells (DCs) are all involved in trophoblast invasion, pregnancy maintenance, and development of pregnancy disorders. Peroxisome proliferator activated receptors (PPARs) are nuclear transcription factors with three known isotypes: PPAR , PPAR¦Â/¦Ä, and PPAR¦Ã. They are expressed in most human organs and their function extends from regulating metabolism, homeostasis, and carcinogenesis to immune response. In the recent years, PPARs have been identified in most reproductive tissues and in all lines of immune cells. Only in few cases, the role of PPARs in reproductive immunology has been elucidated though the role of PPARs in immune answer and immunotolerance is evident. Within this paper we would like to give an update on today¡¯s knowledge about PPARs and immune cells in reproduction and highlight interesting interferences in regard of future therapeutic targets. 1. Introduction Trophoblast invasion at the beginning of pregnancy development is often described in the context of pregnancy complications. The underlying pathophysiology includes elevated macrophage populations hampering trophoblast invasion and inducing trophoblast apoptosis [1, 2]. As another, even bigger part of the innate immune response decidual natural killer (dNK) cells have been identified in promoting trophoblast invasion [3] and reduced numbers of dNK have been reported associated with IUGR [4]. The components of the adaptive immune system present at the fetomaternal interface as the site of immunologic tolerance plays an important role in balancing the maternal immune response to the fetal allograft. For many years a simplified approach to this complex process of immunotolerance was postulated. Thus pregnancy was regarded as a phenomenon of T helper cells subgroup 2 (Th2) going along with inhibition of T helper cells subgroup 1 (Th1) and their cytotoxic effects [5]. However the results of the last years have shown that cytokines associated with Th1 are closely linked to a positive pregnancy outcome [6]. Besides this
%U http://www.hindawi.com/journals/ppar/2013/970276/