Pregnancy: Nature's experimental system. Transient manifestation of immunological diseases in the child.

Major advances in knowledge of immunological diseases have resulted from observation of transient effects on children borne by women with such diseases. The discoveries that in Graves' disease and myasthenia gravis there are IgG antibodies directed against receptors sites are examples of such developments, while "ikiopathic" thrombocytopenic purpura is now accepted as immunological owing to its behaviour during pregnancy. In some instances observations of transient neonatal forms do not correspond with the disease manifestations in the mother. These discrepancies may be due to surgical removal of an organ vital to the disease process; inactivating damage by the disease to such an organ; presence of a blocking antibody of a molecular type not transferred across the placenta; differing tissue-antigen specificity or differing lymphocyte cooperation based on genetic variation. At present there are unexplained observations of fetal/neonatal effects in relation to diabetes mellitus and systemic lupus erythematosus which suggest that study of immunological parameters might be profitable. Determination of the HLA status of mother/fetus pairs may give rewarding clues. In the elucidation of the diseases now proven as antibody-mediated in the antibodies first discovered often turned out to be irrelevant red herrings.