HLA-DR in couples associated with preeclampsia: background and updating by DNA sequencing

The placenta acts as an immunological barrier between the mother and the fetal "graft", allowing two antigenically different organisms to tolerate one another. In placentae from preeclamptic women, we have demonstrated, by an ultrastructural assessment and an immunohistochemical study, a placental barrier breakage leading to the mixing of maternal and fetal antigenically different blood. This condition could be responsible for the triggering of a maternal rejection reaction that we presume to be at the basis of the preeclamptic syndrome. Thus, we have investigated the Human Leukocyte class II DR antigens (HLA-DR), whose role in self and non-self recognition is well known, in women with preeclampsia, their partners and in control couples using the serological Terasaki tecnique. The results showed a statistically significant increase of HLA-DR homozygosity and a reduced antigenic variety in the preeclamptic women and their partners with respect to controls. In this update, we have examined the 2nd exon of the human gene, HLA-DRB1, on the short arm of the chromosome 6 using DNA sequence-based typing (S-BT) PCR in 56 preeclamptic couples and 64 control couples. The results have confirmed the significant excess of HLA-DR homozygosity in couples associated with preeclampsia versus controls. From our results, it emerges that HLA-DR homozygosity and the reduced antigenic variety seem to be associated to a major risk for preeclampsia, which further appears to be a "couple's disease".