Normal Pregnancy and Spontaneous Abortion: Some Immunological Aspects

Around one in five pregnancies end in spontaneous abortion. There are many causes for spontaneous abortion and these are discussed in this thesis. The body of a pregnant women has to tolerate a foetus which receives its genetic material from both parents, and as such is essentially an allograft. Normal pregnancy is therefor a complex challenge to the immune system. The cause of some abortions is unclear and it has been suggested that some abortions may be due to immunological factors. For this study blood samples from normal non pregnant women, normal pregnant women and women undergoing a spontaneous abortion were collected. Isolated peripheral blood lymphocyte cells from the various patient groups were set up in tissue culture. The cells were then stimulated with mitogens and the turn-over of cells and production of immunoglobulins was assessed. Measurement of some cytokine and thyroid antibody levels in the peripheral blood was carried out using enzyme linked immunoabsorbant assays (ELISA). Damage caused by the formation of reactive oxygen species, or free radicals, has been implicated in a number of pathologic conditions. In this study samples from the above groups were assayed for free radical scavenger levels. Compared to normal non-pregnant women, pregnant women were found to have lower IgG levels and raised free radical scavenger levels. Spontaneous aborters also had raised free radical scavenger levels, but no significant difference in IgG levels was detected. Cytokine levels were significantly different in non-pregnant or pregnant women compared to spontaneous aborters. Thyroid antibodies were not detected in the serum of either non pregnant or pregnant women. However, 4 out of 11 recurrent aborters (ie women who had suffered more than three spontaneous abortions) were found to be positive for thyroid antibodies. The significance of these findings is discussed