Purification of pregnancy-specific beta 1-glycoprotein with a monoclonal antibody immunoadsorbent

Highly specific monoclonal antibody demonstrates that pregnancy-specific glycoprotein (PSG) is limited to syncytiotrophoblast in human early and term placenta

Pregnancy specific glycoproteins (PSG) in humans constitute a family of 11 closely related glycoproteins (PSG1-8, PSG11-13) of unknown function(s), which are produced in large amounts by the placenta. As a step toward understanding the biology of PSG, specific monoclonal antibodies (mAbs) against PSG were developed and used to investigate the ultrastructural localization of PSG in the early and term placenta and in first trimester decidua. One mAb, BAP-3, was found to react with all six individually expressed PSGs representing five alternatively spliced forms, but not with any of the seven expressed members of the carcinoembryonic antigen (CEA) subfamily. The BAP-3 epitope is located in the PSG B2 domain. Using the BAP-3 mAb, PSGs were found to be expressed exclusively by the syncytiotrophoblast of first trimester and term villi. The intensity of the staining was much higher in early than in term placenta. All three main cellular compartments involved in the biosynthesis pathway of secreted proteins, i.e. rough endoplasmic reticulum, the Golgi complex and secretory vesicles, were stained for PSG. A second PSG-reactive mAb, BAP-1, also stained the apical plasma membrane of some glandular epithelial cells in first trimester decidua in addition to syncytiotrophoblast. This staining was most likely due to cross-reactivity with biliary glycoprotein (BGP).

Interference of an alpha 2 component in immunological determinations of pregnancy-specific beta 1 glycoprotein in serum

Pregnancy-specific beta 1 glycoprotein (SP1-beta) was purified from human retroplacental blood by sequential anion exchange chromatography, gel chromatography and affinity chromatography. The final preparation appeared to be electrophoretically and immunochemically pure and was in particular free from any component with alpha mobility. The preparation was used as immunogen in rabbits as well as tracer and standard for radioimmunoassay and for cross- and rocket-immunoelectrophoresis. It was shown that this radioimmunoassay procedure, allowed quantitative determination of SP1-beta glycoprotein without interference by the alpha component.

Studies on the elevated amniotic fluid SP1 in Meckel's syndrome: modified glycosylation of SP1

Pregnancy-specific beta 1-glycoprotein (Schwangerschaftsprotein, SP1) is elevated in the amniotic fluid in Meckel's syndrome. In an attempt to clarify this phenomenon, we studied fetal tissues by immunohistochemistry for the distribution of SP1 in normal fetuses and fetuses with Meckel's syndrome. The amount of SP1 was increased in two out of ten Meckel placentae, as semiquantitatively shown by the immunoperoxidase method, but was normal in the rest of the cases. There was no difference in the SP1 distribution or content in the other fetal tissues studied. Fetal cerebrospinal fluid contained only very low levels of SP1 and thus cannot provide a source for elevated amniotic fluid SP1. In addition, binding of amniotic fluid SP1 to concanavalin A (Con-A) was studied in pregnancies with normal fetuses and Meckel's syndrome using affinity chromatography. The proportion not bound to Con-A in normal amniotic fluids decreased with advancing gestation and was lowest when the total SP1 concentrations were highest. An especially low percentage of SP1 not bound to Con A was found in Meckel's syndrome, suggesting an altered carbohydrate structure of SP1 in these amniotic fluids.

Isolation of antihemorrhagic factors in opossum (Didelphis virginiana) serum using a monoclonal antibody immunoadsorbent

The antihemorrhagic factor in opossum (Didelphis virginiana) serum isolated by Sephadex G-200 gel filtration and DEAE A-50 ion exchange chromatography was used as antigen to immunize BALB/c mice. Hybrid cell lines secreting monoclonal antibodies against antihemorrhagic factor were produced by fusion of Sp2/0 myeloma cells with spleen cells of the immunized mice. The ascites fluid was produced in BALB/c mice. The monoclonal antibody in the ascites fluid was partially purified by DEAE A-50 ion exchange and coupled to CNBr-activated isolation of isolation of antihemorrhagic factor. The neutralization capacity of the conventionally isolated antihemorrhagic factor was 14.6 times and the affinity isolated antihemorrhagic factor was 16.8 times that of crude opossum serum. Both antihemorrhagic factors were homogeneous, with one fast migrating band in the area of albumin shown by polyacrylamide gel electrophoresis. However, the antihemorrhagic factor showed one heavy band and one faint band in SDS-polyacrylamide electrophoresis, as well as in isoelectric focusing. The molecular weight of the heavy band was estimated to be 65,000 with a value of p1 4.8 and the faint band was 57,000 with a value of pI 4.1.