Immune reactions of normal pregnancy

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.

Preliminary characterization of isoimmunogenic placental antigens in the rabbit

By isoimmunization of adult virgin female rabbits with rabbit placental extracts we have demonstrated the production of humoral antibody against two antigens, Ag-1 and Ag-2. Neither antigen is a normal serum protein, nor are they allotype proteins. Ag-1 has an alpha-2 mobility and a molecular weights of about 400,000. Ag-2 exhibits a gamma mobility but was not characterized. The antibody activity directed to Ag-1 in immune sera was the complement-fixing IgG fraction. Direct fluorescence-labeled antibody technique revealed that Ag-1 is a ubiquitous intracellular antigen primarily localized in the nucleus. The fast-growing, SV-40 virus-transformed rabbit kidney cell line (TRK-1) expressed much higher levels of Ag-1 than the slow-growing, non-transformed normal rabbit kidney cell line (LLC-RK1). The possibility that elevation of Ag-1 production is associated with rapid cell proliferation is discussed.

Placenta, transcortin, and localized immune response

The syncytiotrophoblastic cells of the human placenta contain a cytoplasmic protein recognized by fluorescein-labeled transcortin-specific antibody. Purification of this protein from human placenta, by those methods employed for the purification of human plasma transcortin, yielded a protein that exhibited antigenic and biochemical similarity to plasma transcortin. Placental transcortin differs from plasma transcortin in that it has a smaller sedimentation coefficient (3S vs 3.75S) and binds cortisol less strongly. This purified protein is able to block the phytohemagglutinin response of maternal lymphocytes even more than serum transcortin. It is postulated that the biological role may be that of inhibiting the maternal cell-mediated immune response to the presence of the antigenic conceptus.