Blood SC5b-9 complement levels increase at parturition during term and preterm labor.

Journal of reproductive immunology

PubMedID: 25868739

Segura-Cervantes E, Mancilla-Ramirez J, Zurita L, Paredes Y, Arredondo JL, Galindo-Sevilla N. Blood SC5b-9 complement levels increase at parturition during term and preterm labor. J Reprod Immunol. 2015;.
We explored the hypothesis that complement, an innate and adaptive immune effector, is active in the plasma of parturient women and is deposited on fetal membranes collected after delivery. A cross-sectional study was designed to evaluate complement activity at parturition. Pregnant women (n=97) between 15 and 41 years of age were enrolled in a hospital protocol during the perinatal period to assess both SC5b-9 complement activity in blood and complement deposition on fetal membranes during parturition. Soluble SC5b-9 complement activity in plasma fractions was measured using a standard enzyme-linked immunosorbent assay (ELISA) that included specific anti-complement antibodies. Complement deposition on membranes was analyzed using immuno-dot blots and immunohistochemistry. Soluble SC5b-9 complement complex levels were increased in the plasma of women during term labor (TL; median 3361; range 1726-5670ng/mL), preterm labor (PL; median 2958; range 1552-7092ng/mL), and preterm premature rupture of membranes (PPROM; median 2272; range 167-6540ng/mL) compared with pregnant women who were not in labor (P; median 1384; range 174-4570ng/mL; P<0. 001, Kruskal-Wallis test). Active complement, as assessed by the C9 neo-antigen in C5b-9 complexes, was deposited on fetal membranes, with no difference between term and preterm delivery. The deposition of active complement on fetal membranes was confirmed by immunohistochemistry. Women who underwent non-labor-indicated Cesarean sections did not exhibit complement deposition. Soluble SC5b-9 complement complex levels increased in the plasma of women during parturition, and complement C5b-9 complexes were deposited on fetal membranes.