Behaviour of immune complexes and the complement system in normal pregnancy and pre-eclampsia

Area of Science:

• Immunology
• Obstetrics
• Biochemistry

Background:

• Circulating immune complexes (IC) and complement (C) system activity are implicated in pregnancy physiology and pathology.
• Understanding their dynamics in normal pregnancy versus pre-eclampsia is crucial for diagnosis and management.

Purpose of the Study:

• To quantitatively assess circulating immune complexes (IC) in women with normal pregnancy and pre-eclampsia.
• To investigate the behavior of the complement (C) system during normal pregnancy and pre-eclampsia.

Main Methods:

• Quantitative analysis of circulating immune complexes (IC) in 286 normal pregnancies, 20 post-partum women, and 30 pre-eclamptic women.
• Monitoring of complement (C) system components (C1-INH, C1s, C1q, C3, C5, C9, properdin factor B, CH50, C3d) throughout gestation and post-partum.

Main Results:

• Immune complexes (IC) were low in early normal pregnancy, decreasing further in later trimesters, contrasting with their constant presence in pre-eclampsia.
• A significant difference (p < 0.0001) in IC incidence was observed between third-trimester normal pregnancy and pre-eclampsia.
• Complement (C) system showed decreased C1 components and increased C3, C5, C9, and properdin factor B during normal pregnancy, with elevated C3d in both normal pregnancy and pre-eclampsia, suggesting complement activation.

Conclusions:

• Circulating immune complexes (IC) are a key differentiator between normal pregnancy and pre-eclampsia.
• Complement (C) system activation occurs in both normal pregnancy and pre-eclampsia, potentially masked by increased synthesis.
• Alloantibodies and IC may drive complement activation in normal pregnancy and pre-eclampsia, respectively.