Circulating Innate Lymphoid Cells Exhibit Distinctive Distribution During Normal Pregnancy

Area of Science:

• Reproductive Immunology
• Innate Immunity

Background:

• Innate lymphoid cells (ILCs) are crucial for successful pregnancy.
• Sex hormones (estradiol, progesterone) fluctuate during pregnancy, impacting immune responses.
• The precise role of ILC subset distribution and sex hormone interplay in human pregnancy remains unclear.

Purpose of the Study:

• To investigate the dynamic changes in circulating ILC subsets during pregnancy.
• To explore the association between ILC subset distribution and plasma sex hormone levels.
• To identify sex hormone receptors on human circulating ILCs.

Main Methods:

• Collected peripheral blood from non-pregnant, early-pregnant, and late-pregnant women.
• Measured plasma estradiol and progesterone using radioimmunoassay.
• Analyzed ILC subsets (ILC1, ILC2, ILC3, total ILCs) and sex hormone receptor expression on ILC2s via flow cytometry.

Main Results:

• Circulating ILC proportions and subset distribution changed dynamically throughout pregnancy.
• Late-pregnant women showed significantly higher total ILCs, predominantly ILC2s, while ILC3s decreased compared to non-pregnant women.
• Plasma estradiol and progesterone levels increased with advancing pregnancy, correlating with elevated progesterone receptor expression on ILC2s.

Conclusions:

• This study reveals novel patterns of circulating ILC subset distribution during human pregnancy.
• It demonstrates the presence of progesterone receptors on human circulating ILC2s for the first time.
• Findings suggest that estradiol and progesterone levels may influence circulating ILC subset distribution, highlighting their interplay in pregnancy.