Frozen sections of human placenta were examined for the presence of four human pregnancy proteins, pregnancy-associated plasma proteins A and C (PAPP-A and PAPP-C), human chorionic somatomammotropin (hCS), and pregnancy zone protein (PZP), by the indirect immunofluorescence technique. Monospecific rabbit antiserums to PAPP-A, PAPP-C and hCS all stained the trophoblast cytoplasm equivalently in a continuous layer, usggesting that the same trophoblast cells synthesize all three pregnancy proteins. In contrast, PZP was localized in blood vessel walls, parenchymal structures within the villous, as well as in the trophoblast cytoplasm. Its distribution in the latter was relatively inhomogeneous, tending to be more intense on the basement membrane side.
Three human pregnancy-associated plasma proteins (PAPPs), which were detected only during pregnancy with appropriately absorbed antisera to pregnancy plasma, were purified from third trimester plasma. The authors employed combinations of sequential DEAE-cellulose and hydroxylapatite chromatography; Sephadex G-100, G-200 and Sepharose 6B gel filtration; isoelectric focusing; and/or ammonium sulfate salting out. Each final product was shown to contain only one PAPP, to be immunologically free of most normal plasma proteins, and to have specific activities 100- to 145-fold greater than in the original pregnancy plasma. Rabbits immunized with these preparations responded with antisera which became mono-specific to their respective PAPP after appropriate absorption. PAPP-D, the one with low molecular weight (20,000), was shown immunologically to represent human placental lactogen. Another, PAPP-C, has been found to be identical to the pregnancy-specific β1-glycoprotein described by Bohn (designated by him as SP1 protein). The other, PAPP-A, of molecular weight 750,000, is distinct from the other two pregnancy-associated proteins of Bohn (designated SP2 and SP3), as well as the α2-pregnoglobulin of Berne. Since the latter and SP3 proved to be identical immunologically, and since it has been reported that SP3, Xh factor, pregnancy-associated globulin (PAG or Pal), and the pregnancyzone proteins are identical to each other, PAPP-A may represent a new pregnancy-specific protein. None of the PAPPs were detected in sera from 102 patients with various malignancies.
A quantitative and standardized enzyme-linked immunosorbent assay is described which uses lyophilized antigen-coated disks for the detection of human antibodies to Toxoplasma gondii. It does not require serial dilution of the test specimen, and the objective absorbance readings are converted into international units per milliliter traceable to the World Health Organization's reference standard preparation of toxoplasma antibodies. It was shon.-
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