In normal pregnancy, villous cytotrophoblast and syncytiotrophoblast do not express HLA Class I and Class II molecules, while invasive extravillous trophoblast only express class I HLA-C and the atypical class Ib antigens, HLA-G, -E and -F. Inadequate maternal tolerance of invasive trophoblast has been proposed as a possible immunologic trigger of poor trophoblast invasion and subsequent occurrence of pre-eclampsia.
Based on genotyping and full gene sequencing of HLA-G in a large number of cases and controls (n > 900), the present study, which to our knowledge is the largest and most comprehensive performed, investigated the association between the HLA-G 14-bp ins/del (rs66554220) and HLA-E polymorphisms in mother and newborn dyads from pregnancies complicated by severe preeclampsia/eclampsia and from uncomplicated pregnancies.
Our data indicate that in addition to Foxp3(+) Treg cells, CD4(+) T cells acquire HLA-G from decidual DCs and may play an important role in immune tolerance induction in pregnancy, a process which is impaired in pre-eclampsia.
Recent findings regarding aspects of HLA-G polymorphism, the possible significance of this polymorphism in respect to HLA-G function and certain complications of pregnancy (such as pre-eclampsia and recurrent spontaneous abortions (RSA)) are discussed together with possible importance to IVF.
The frequency of HLA-G polymorphism in these samples was not significantly different from those of normal controls, indicating that maternal HLA-G polymorphism is not associated with the risk for pre-eclampsia in this Chinese Han population.