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Updated: Jun 19, 2026

Detection of Ligand-activated G Protein-coupled Receptor Internalization by Confocal Microscopy
Published on: April 9, 2017
Progesterone in pregnancy; receptor-ligand interaction and signaling pathways
Julia Szekeres-Bartho1, Melinda Halasz, Tamas Palkovics
1Department of Medical Microbiology and Immunology, Medical School, Pecs University, H-7624 Pecs, Szigeti ut 12, Hungary. szjuli@main.pote.hu
Abstract:
Progesterone is indispensable in creating a suitable endometrial environment for implantation, and also for the maintenance of pregnancy. Successful pregnancy depends on an appropriate maternal immune response to the fetus. Along with its endocrine effects, progesterone also acts as an "immunosteroid", by contributing to the establishment of a pregnancy protective immune milieu. Progesterone plays a role in uterine homing of NK cells and upregulates HLA-G gene expression, the ligand for NK inhibitory and activating receptors. At high concentrations, progesterone is a potent inducer of Th2-type cytokines as well as of LIF and M-CSF production by T cells. A protein called progesterone-induced blocking factor (PIBF), by inducing a Th2-dominant cytokine production mediates the immunological effects of progesterone. PIBF binds to a novel type of the IL-4 receptor and signals via the Jak/STAT pathway, to induce a number of genes, that not only affect the immune response, but might also play a role in trophoblast invasiveness.
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