An immunoprecipitation-dissociation technique for large scale antibody purification and an antigen consumption electroimmunoassay for antibody quantitation. A model study with antibodies to pregnancy zone protein

Comparison of different antibody preparations against pregnancy-associated plasma protein-A (PAPP-A) for use in localization and immunoassay studies

Four antibody preparations against pregnancy-associated plasma protein (PAPP-A) were compared in order to find an explanation for the contradictory results published on tissue localization, clinical usefulness and biological function of PAPP-A. One of the preparations studied was a rabbit anti-PAPP-A antiserum which has been offered for general scientific use (Bischof et al. 1979). Only the IgG fraction of anti-PAPP-A antisera which appeared to be monospecific and had been further absorbed with fetal connective tissue gave specific uniform staining of the cytoplasm of the syncytiotrophoblast exclusively. Circulating PAPP-A could not be detected by RIA employing this IgG preparation in the non-pregnant state, or before 18 days after conception. Circulating PAPP-A could be detected in all seven pregnant women studied within 4 weeks after conception. Identical results were obtained with a commercially available IgG fraction against PAPP-A.

Immunohistochemical aspects of immunological cross-reaction and masking of epitopes for localization studies on pregnancy-associated plasma protein A

The influence of antibody absorption procedures and proteolytic pre-treatment of formaldehyde-fixed placental tissue on the localization of pregnancy-associated plasma protein A by immunoperoxidase technique was examined. Apparently monospecific IgG fraction of the anti-plasma protein applied directly on fixed tissue resulted in staining of connective tissue and a thin apical rim of the syncytiotrophoblast. Further absorption of the antibody with foetal connective tissue abolished this staining reaction. Pre-treatment of the fixed placental tissue with trypsin prior to application of the antibody, which had been absorbed with connective tissue, resulted in staining within the cytoplasm of the syncytiotrophoblast exclusively. Identical staining was seen when this IgG preparation was used directly on frozen placental tissue. The results point to the importance of the specificity of the antibody preparations and of proteolytic unmasking of epitopes when fixed tissues are used for localization studies of pregnancy-associated plasma protein A by immunoperoxidase technique.

Production of antibody against C3c epitopes which are inaccessible on native C3

Anti-C3c antiserum was induced by immunizing rabbits with autologous erythrocytes coated with human C3b/C3bi. By absorption with human plasma this antiserum was rendered specific for C3c epitopes which are not expressed on native C3. This specificity may be analogous to that of immunoconglutinin.

Circulating levels of pregnancy zone protein: normal range and the influence of age and gender

Serum levels of pregnancy zone protein (PZP) were measured in 506 apparently normal males and 329 normal non-pregnant females, the age range being 18 to 70 years. The estimations of PZP were performed by sensitive radio-rocket-line immunoelectrophoresis. The distribution of the data had a marked positive skew in both sexes which was reduced following logarithmic transformation. Serum concentrations in both men and women were found to increase significantly with advancing age. This increase and the mean concentrations were significantly higher in females.

A method for preparation of immunosorbents by direct coupling of dissociated immune complexes

A simple and rapid method of preparing immunosorbents by use of isolated immune complexes is described. Dissociated immune complexes may be directly coupled to activated Sepharose and an immunosorbent gel with complementary molecular populations of immunospecifically purified ligands is obtained. The antigen binding capacity of insolubilized antibodies was about 50% of the antigen bound at equivalence using liquid phase precipitation. The batch technique described may be scaled up and the only limitation is the availability of the ligands. The usefulness of the technique is illustrated in two model systems.

Affinity chromatographic purification of the pregnancy zone protein

An immunospecific affinity chromatographic method for purification of human pregnancy zone protein (PZP) directly from serum is described. Highly purified goat-anti-human PZP-immunoglobulin was applied as a ligand. Recovery of PZP varied from 56--75%. The impurities constituted maximally 5--10% of the total protein in the eluate. The purification factor was approximately 100.