Immunogenetics of trophoblastic tumours.

The fetus is an allograft foreign to the mother by the hemizygous set of paternal alleles. In a randomly mating population the mother may be incompatible with the fetus at any locus and the chance of incompatibility is increased according to the number of alleles at that locus. The persistence of the normal human fetal allograft is a puzzle that continues to intrigue biologists. The immunobiology of the trophoblast was debated at length at a symposium held in Cambridge in 1973. In a preface to the proceedings the editors (Edwards, et al, 1975) ventured their personal opinion that 'the properties of the trophoblast as a natural filter currently offer the most critical single explanation for fetal survival'. To search for a single explanation of such complex biological interactions as those involved in the fetomaternal relationship is perhaps rather ambitious. The problem of the persistence of trophoblast-natural, invasive, or malignantmust be regarded as a sequel of maternal conditioning to the normal products of conception. This may affect her role as host to any supervening malignantly transformed trophoblast.