Progesterone as an immunologic blocking factor in human pregnancy serum

Area of Science:

• Immunology
• Endocrinology
• Reproductive Biology

Background:

• Pregnancy involves significant hormonal changes, including elevated levels of estriol and progesterone.
• Lymphocyte reactivity is crucial for immune responses, and its modulation during pregnancy is of interest.

Purpose of the Study:

• To investigate the effects of estriol and progesterone on lymphocyte reactivity.
• To determine the role of progesterone in the serum's inhibitory activity on lymphocyte cytotoxicity during late pregnancy.

Main Methods:

• Lymphocytes from non-pregnant women were incubated with varying concentrations of estriol and progesterone.
• Cytotoxic effects on human embryonic fibroblast cells were measured.
• Pregnancy sera, both complete and progesterone-depleted, were used to assess inhibitory activity.

Main Results:

• Progesterone demonstrated a significant inhibitory effect on lymphocyte cytotoxicity at physiological concentrations.
• Estriol did not show a significant inhibitory effect.
• Depletion of 95% progesterone from pregnancy sera resulted in an 80% reduction in inhibitory activity.

Conclusions:

• Progesterone levels during pregnancy are sufficient to suppress lymphocyte reactivity.
• Progesterone is the primary factor responsible for the serum's inhibitory effect on lymphocyte cytotoxicity in late pregnancy.