Table 1:

Overview of local and peripheral immune pathogenesis in preeclampsia

Immune Pathway	Maternal-fetal Interface	Peripheral Blood
Complement cascade
Classical pathway	C1q deposition in chorionic villi, placental blood vessel endothelia90–93	Lower levels of C1q93
Lectin pathway	Higher C4d, ficolins H, L deposition in syncytiotrophoblast90,94–96	Lower levels of C4, Ficolins H, L93,96–98 Higher levels of C4d24,99
Alternative pathway	C3 deposition in decidua tissue, villous endothelial cells91,100–102	Higher levels of fragment Bb103
C3a and C5a (anaphylatoxins)	Lower C3a receptor and conflicting results of higher and lower C5a expression in preeclampsia18	Majority of studies with higher C3a18,19 Reports of both higher19 and similar C5a93
Terminal MAC (C5b-9)	Increased MAC deposition in stroma and syncytiotrophoblast26,92	Most demonstrate higher MAC19,22
Complement regulatory proteins	DAF and CD59 upregulated90
T helper bias
Th1	Increased TNFα49,50	Increased TNFα49,50
Th2	Reduction in IL-449,50	Reduction in IL-449,50
Regulatory T cells (Treg)	Reduced FoxP3 and IL-10 expression in first trimester104 and at delivery105,106,107 Decreased Treg clonal expansion47,108	Decrease in Treg proportion105,109 and suppressive capacity44 Lower activation of memory Treg35
Th17	Increased proportion of CD4 T cells (Collier, unpublished)	Upregulation in Th1749

DAF= decay accelerating factor

MAC= membrane attack complex

Treg= regulatory T cells