Elevated serum levels in human pregnancy of a molecule immunochemically similar to eosinophil granule major basic protein.

Abstract

Serum levels of a molecule immunochemically similar to eosinophil granule major basic protein (MBP) are elevated in pregnant women throughout gestation. MBP levels increase during gestation and plateau at 7500 ng/ml by the 20th wk (> 10-fold above normal). Levels return to normal after delivery, with a T1/2 [half-life] of 13.7 day. The following observations have raised the possibility that the eosinophil is not the source of the MBP in pregnancy serum. No correlation between serum MBP level and peripheral blood eosinophil count exists in pregnant women, in contrast to previous studies of patients with eosinophilia. Levels of 3 other eosinophil-associated proteins are normal or low in pregnancy sera, whereas the serum levels of these proteins are elevated in patients with eosinophilia. The slopes of dose-response curves for pregnancy sera and MBP standards differ in the double-antibody radioimmunoassay. The molecule in pregnancy serum elutes from Sephadex G-50 columns at the void volume, while eosinophil granule MBP and the MBP in serum of patients with eosinophilia elute at a volume consistent with the previously established MW of 9300. The MBP in pregnancy serum could be derived from a source other than the eosinophil [i.e., placenta].