Immune Modifications in Fetal Membranes Overlying the Cervix Precede Parturition in Humans

Area of Science:

• Reproductive immunology
• Human parturition
• Maternal-fetal interface immunology

Background:

• Parturition is characterized by intrauterine inflammation and cytokine release at the maternal-fetal interface.
• The zone of altered morphology (ZAM) in fetal membranes near the cervix exhibits changes before labor onset.

Purpose of the Study:

• To investigate local immune changes within the ZAM preceding parturition.
• To understand the molecular and cellular events initiating labor.

Main Methods:

• Transcriptome analysis
• Flow cytometry
• Electron microscopy
• Immunohistochemistry

Main Results:

• The ZAM shows localized gene expression shifts and lymphocyte activation.
• Fetal HLA-A, -B, and -C determinants become exposed to the maternal immune system in the ZAM.
• A graft rejection-like process occurs, involving cytotoxic decidual NK cell activation and M2-like macrophage decline.
• Acute inflammation follows these initial immune modifications.

Conclusions:

• Local immune remodeling, not acute inflammation, initiates parturition.
• The ZAM is a critical site for immune adjustments at the maternal-fetal interface before labor.
• These findings redefine the early stages of human parturition.