Correlation between oral sex and a low incidence of preeclampsia: a role for soluble HLA in seminal fluid?

The involvement of immune mechanisms in the aetiology of preeclampsia is of ten suggested. Normal pregnancy is thought to be associated with a state of tolerance to the foreign antigens of the fetus, whereas in preeclamptic wo men this immunological tolerance might be hampered. The present study shows that oral sex and swallowing sperm is correlated with a diminished occurre nce of preeclampsia which fits in the existing idea that a paternal factor is involved in the occurrence of preeclampsia. Because pregnancy has many s imilarities with transplantation, we hypothesize that induction of allogene ic tolerance to the paternal HLA molecules of the fetus may be crucial. Rec ent data suggest that exposure, and especially oral exposure to soluble HLA (sHLA) or HLA derived peptides can lead to transplantation tolerance. Simi larly, sHLA antigens, that are present in the seminal plasma, might cause t olerance in the mother to paternal antigens. In order to test whether this indeed may be the case, we investigated whether sHLA antigens are present i n seminal plasma. Using a specific ELISA we detected sHLA class I molecules in seminal plasma. The level varied between individuals and was related to the level in plasma. Further studies showed that these sHLA class I molecu les included classical HLA class I alleles. such as sHLA-A2. -B7. -B51. -B3 5 and sHLA-A9. Preliminary data show lower levels of sHLA in seminal plasma in the preeclampsia group, although not significantly different from the c ontrol group. An extension of the present study is necessary to verify this hypothesis. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.