Cytokines in human reproduction

Cytokines are regulatory peptides or glycoproteins that can be produced by virtually every cell type in the body and have pleiotropic regulatory effects on hematopoietic, endocrine, nervous and immune systems. Unlike hormones, cytokines usually act as intercellular (paracrine) and/or intracellular (autocrine) signals. During the last 15 years the concepts of the role and functioning of reproductive organs during human pregnangcy have been changing. There is much evidence that cytokines play a very important role in the reproduction ie, ovarian follicular development, embryo implantation, endometrial development, and trophoblast growth and differentiation by modulating immune and endocrine systems. Recent data demonstrate that oozyte, granulosa cell and theca cell produce a network of cytokines that interact at various levels in modulating the follicular development and follicular atresia. Cytokines mediate the endocrine and immune systems of he maternal body, fetus and placenta. For example, Th2 type cytokines such as IL-4, IL-6, and IL-10, which seems to be of prime importance in the maintenance of pregnancy, are produced by trophoblasts and decidual Th2 cells. Th2 cytokines induce hCG release from trophoblasts. As a result, hCG induces the production of progesterone by the corpus luteum so that Th2 cells can be stimulated to differentiate from Th0 cells by progesterone. Thus, cytokines and hormones cross-talk each other. From the early stage of implantation until the expulsive phase of delivery, the cross-talk between immune system and endocrine system via cytokines is critical for successful gestation. In this study, the author review the characteristics of cytokines in the immune and endocrine systems in the human reproduction.