Preeclampsia and oral sex

So I'm teaching cardiovascular anatomy and physiology right now, which is funny because Rob is teaching the drugs for that system in pharmacology at the same time. I was reading up on preeclampsia, which is a type of hypertension that can develop during pregnancy, looking for hypotheses for causes. I'm doubly interested because I've recently stumbled upon a potential regulatory protein which could be associated with the disease. To make a long story short there is definitely a strong immune involvement, and a problem in the placental interface although the details are surprisingly not well fleshed out (to an outsider anyways). I was also somewhat amused to find out that there is a putative protective role of oral sex and swallowing of seminal fluids for preeclampsia. The idea being that HLA and HLA-derived peptides may tolerize the mother to the foreign antigens of the fetus in the same way that we tolerize other food-related antigens passing through the gut. While this paper certainly isn't definitive, a correlation at best, the treatment has few side effects, so might as well err on the safe side:

"we investigated whether sHLA antigens are present in 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 molecules included classical HLA class I alleles, such as sHLA-A2, -B7, -B51, -B35 and sHLA-A9. Preliminary data show lower levels of sHLA in seminal plasma in the preeclampsia group, although not significantly different from the control group."