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This article is part of the supplement: Preterm Birth - Interdisciplinary research from the Preterm Birth and Healthy Outcomes Team (PreHOT)

Open Access Research

Maternal circulating leukocytes display early chemotactic responsiveness during late gestation

Nardhy Gomez-Lopez12, Satomi Tanaka1, Zoya Zaeem1, Gerlinde A Metz3 and David M Olson1*

Author Affiliations

1 Departments of Obstetrics and Gynecology, Pediatrics and Physiology, University of Alberta, Edmonton, T6G 2S2, Canada

2 Department of Obstetrics and Gynecology, School of Medicine, Perinatology Research Branch, Wayne State University, Detroit, MI, 48201, USA

3 Canadian Centre for Behavioral Neuroscience, University of Lethbridge, Lethbridge, T1K3M4, Canada

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BMC Pregnancy and Childbirth 2013, 13(Suppl 1):S8  doi:10.1186/1471-2393-13-S1-S8

Published: 31 January 2013

Abstract

Background

Parturition has been widely described as an immunological response; however, it is unknown how this is triggered. We hypothesized that an early event in parturition is an increased responsiveness of peripheral leukocytes to chemotactic stimuli expressed by reproductive tissues, and this precedes expression of tissue chemotactic activity, uterine activation and the systemic progesterone/estradiol shift.

Methods

Tissues and blood were collected from pregnant Long-Evans rats on gestational days (GD) 17, 20 and 22 (term gestation). We employed a validated Boyden chamber assay, flow cytometry, quantitative real time-polymerase chain reaction, and enzyme-linked immunosorbent assays.

Results

We found that GD20 maternal peripheral leukocytes migrated more than those from GD17 when these were tested with GD22 uterus and cervix extracts. Leukocytes on GD20 also displayed a significant increase in chemokine (C-C motif) ligand 2 (Ccl2) gene expression and this correlated with an increase in peripheral granulocyte proportions and a decrease in B cell and monocyte proportions. Tissue chemotactic activity and specific chemokines (CCL2, chemokine (C-X-C motif) ligand 1/CXCL1, and CXCL10) were mostly unchanged from GD17 to GD20 and increased only on GD22. CXCL10 peaked on GD20 in cervical tissues. As expected, prostaglandin F2α receptor and oxytocin receptor gene expression increased dramatically between GD20 and 22. Progesterone concentrations fell and estradiol-17β concentrations increased in peripheral serum, cervical and uterine tissue extracts between GD20 and 22.

Conclusion

Maternal circulating leukocytes display early chemotactic responsiveness, which leads to their infiltration into the uterus where they may participate in the process of parturition.