Detection of soluble HLA-G levels in maternal serum can be predictive for a successful pregnancy

Abstract

THE IDENTIFICATION of HLA-G on placental cytotrophoblast cells opened new insights in defining the initial trigger by which the maternal immune system recognizes the fetal allograft and emits growth signals to the feto-placental unit. The presence of an alternatively spliced mRNA giving rise to secreted HLA-G class I antigens makes these molecules very important candidates for explaining peripheral maternal immunostimulation and immunosuppression during pregnancy. In many cases, especially during transplantation, soluble MHC antigens have been shown to exert immunosuppressive activity. Therefore, during pregnancy, the maternal organism is expected to respond to the semior fully allogeneic fetus in a similar way, where soluble antigens during the first 2 months of gestation elaborate messages that are positive to fetal growth (immunostimulation) and thereafter, equilibrates fetal development by inducing specific immunosuppression. Disability of the maternal organism to elaborate these two types of reaction results in embryo loss, mainly during the first trimester of pregnancy, which in previous studies has been correlated with expression of class II MHC antigens on trophoblasts, normally absent from these cells throughout pregnancy. In the present study, using the monomorphic W6/32 and 7H3 antibodies, we define the levels of soluble HLA-G and HLA-DR respectively in the serum of healthy women before, during, and after pregnancy and compare them to cases of first-trimester fetal abortions of unknown etiology. Taking into consideration the obtained results, along with similar findings from animal experimental abortion models, we conclude that the levels of soluble class I/II in the maternal serum can be predictive to a successful pregnancy outcome.