Immunological and molecular genetic studies on trophoblast membrane proteins

Nickson, Debra Ann (1985) Immunological and molecular genetic studies on trophoblast membrane proteins. PhD thesis, University of Glasgow.

Abstract

1. In recent years the plasma membrane components of the human trophoblast have attracted increasing interest. Many investigators have wondered about the extent to which trophoblast components may contribute to the outcome of pregnancy, in particular the extent to which genetic variation in trophoblast components contributed to diseases of pregnancy. The HLA transplantation antigens play a major role in the success of organ transplants, HLA determinants have been detected on the extravillous cytotrophoblast of the placenta. The role these determinants play in the outcome of pregnancy is unknown, as is the relationship of these placental HLA determinants to the classic HLA A and B allotypes. Classical HLA determinants are not detected on the placental syncytiotrophoblast microvilli. Placental alkaline phosphatase is the major external component of placental microvilli and is known to show genetic variation, having three common alleles and also 15 rare alleles which account for 2.5% of the PLAP phenotypes. The function of this genetic variation to date is unknown. Though trophoblast specific antigens have been identified xenogeneically no conclusive work has been done to detect antibodies in maternal sera to trophoblast surface components. 2. This thesis describes two lines of investigation. The first was a serological approach to find out whether placental surface determinants are recognised by the maternal immune system. For this, syncytiotrophoblast plasma membranes prepared from term placentae were tested in a passive haemagglutination assay for their ability to function as antigenic determinants with term maternal sera. The second was a molecular genetic approach involving the creation of placental cDNA libraries. These libraries were screened for cDNA clones which would aid in the characterisation of (a) the histocompatibility antigens present in the cytotrophoblast cells of the term chorionic plate and, (b) the enzyme placental alkaline phosphatase (PLAP) which has a high level of genetic polymorphism and is quantitatively the major cell membrane protein of the syncytiotrophoblast. 3. Using the passive haemagglutinin assay, agglutinins against trophoblast components were detected in term maternal sera at titres above those of non-pregnant control sera. These agglutinin titres were independant of the family relationship between individual sera and trophoblast samples. They were uneffected by adsorption with excess packed fetal or paternal red blood cells or paternal lymphocytes. The agglutinins of both normal control and term maternal sera were found to elute in the macroglobulin fraction of serum having a mw of >350Kd and were shown to be a component of euglobulin precipitates. The agglutinin titres remained in sera and were unaffected by the adsorption of IgM and IgG from the sera. It was concluded that these agglutinins were not a maternal antibody response against trophoblast surface components. 4. mRNA prepared from syncytiotrophoblast cells, and from purified cytotrophoblast cells of the chorionic plate were analysed by in vitro translation and immunoprecipitation. The major polypeptide synthesised from syncytiotrophoblast mRNA was hPL, accounting for 15-20% of the translated polypeptides. In cytotrophoblast mRNA preparations this polypeptide accounted for only 1-5% of the synthesised polypeptides. Immunoprecipitation of the in vitro translated polypeptides from syncytiotrophoblast mRNA using anti-PLAP specifically precipitated polypeptides of 56Kd and 58Kd. Both PLAP and hPL mRNA levels were shown to increase with gestational age.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: Genetics, Molecular biology, Immunology
• Date of Award: 1985
• Depositing User: Enlighten Team
• Unique ID: glathesis:1985-76565
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 19 Nov 2019 14:08
• Last Modified: 19 Nov 2019 14:08
• URI: https://theses.gla.ac.uk/id/eprint/76565