Quantification and characterization of pregnancy-associated complexes of angiotensinogen and the proform of eosinophil major basic protein in serum and amniotic fluid.
BACKGROUND
The proform of eosinophil major basic protein (ProMBP) exists in serum from pregnant women complexed with a variable fraction of angiotensinogen (Ang). A subfraction further binds complement C3dg in a 2:2:2 complex. The function, physiology, and clinical importance of ProMBP complexes are unknown, and the specific quantification of these complexes has not been possible.


METHODS
We developed an ELISA for the ProMBP/Ang complexes, using a monoclonal antibody against ProMBP for capture and a chicken anti-human Ang antiserum for detection. Calibrators were standardized with WHO IRP 78/610 for pregnancy proteins in the assay range 0.95-15.6 mIU/L.


RESULTS
The concentrations of ProMBP/Ang complexes in serum of nonpregnant blood donors (n = 79) were log-normally distributed with a central 95th interval of 985-3655 mIU/L. In pregnancy, mean serum concentrations were increased from week 7, and the concentrations reached term concentrations in week 18. ProMBP/Ang complexes eluted in gel filtration as a broad peak with a molecular mass of approximately 230 kDa. The concentration of ProMBP/Ang/C3dg increased during blood coagulation, suggesting that the ProMBP/Ang/C3dg complex may be a marker of complement activation.


CONCLUSIONS
ProMBP/Ang complexes are present in serum from nonpregnant persons as well as pregnant women, and the direct assays described here will make it possible to study the biochemistry and the clinical significance of different ProMBP complexes in pathological conditions and pregnancy.
Christiansen
M
M
Department of Clinical Biochemistry, Statens Serum Institut, 5 Artillerivej, Copenhagen DK 2300 S, Denmark. mic@ssi.dk
Jaliashvili
I
I
Overgaard
M T
MT
Ensinger
C
C
Obrist
P
P
Oxvig
C
C
D000653:Amniotic Fluid / Q000378:metabolism*; D000808:Angiotensinogen / Q000097:blood / Q000378:metabolism*; D001782:Blood Donors; D001798:Blood Proteins / Q000378:metabolism*; D002846:Chromatography, Affinity; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D004797:Enzyme-Linked Immunosorbent Assay; D047091:Eosinophil Granule Proteins; D004804:Eosinophils / Q000378:metabolism*; D005260:Female; D006801:Humans; D008297:Male; D011247:Pregnancy / Q000097:blood / Q000378:metabolism*; D011498:Protein Precursors / Q000097:blood; D012016:Reference Values; D015203:Reproducibility of Results; D012260:Ribonucleases; D012680:Sensitivity and Specificity
D001798:Blood Proteins; D047091:Eosinophil Granule Proteins; D011498:Protein Precursors; D000808:Angiotensinogen; D012260:Ribonucleases