Detection of antibodies in pregnancy serum reacting with isolated placental basement membrane collagen

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Abstract
Adsorption of human IgG from pregnancy sera to placental basement membrane collagen could be demonstrated by an in-vitro assay. Polystyrene tubes were coated with purified type IV collagen and incubated with serum samples. Bound human IgG was detected using 125I-labelled antihuman IgG. Median adsorption levels were 4000 (inter-quartile range 2500-9500) cpm/ml serum in 25 uncomplicated pregnancies and 21000 (interquartile range 14500-44500) cpm/ml serum in 14 pre-eclamptic women. Specificity of the adsorption reaction could be demonstrated using uncoated tubes and collagenase treated coated tubes, which all showed low binding. In competition experiments with dissolved collagen fractions (type I, III, IV) most effective displacement of binding was observed with type IV collagen. This indicates collagen selectively of the adsorption reaction of human IgG to basement membrane collagen. Our in-vitro studies support immunohistochemical findings of IgG binding to trophoblastic basement membranes and their ultrastructural abnormalities detected in pre-eclamptic placenta.