HLA-G and its role in implantation (review).
BACKGROUND
Human leukocyte antigen G (HLA-G) is thought to play a key role in implantation by modulating cytokine secretion to control trophopblastic cell invasion and to maintain a local immunotolerance.


METHODS
The literature is reviewed to provide a description of the genetic background, properties of the protein, and the function of HLA-G. Data are presented on potential clinical applications of HLA-G including the use of evaluation of HLA-G gene polymorphisms in the diagnosis of patients experiencing recurrent pregnancy loss and evaluation and testing of soluble HLA-G (sHLA-G) in embryo culture media for the selection of embryos for transfer after in vitro fertilization (IVF).


RESULTS
The literature supports a central role of HLA-G for successful implantation. Of couples experiencing recurrent pregnancy loss, 32% demonstrated the -1725G HLA-G polymorphism. Our data showed that when embryos were selected for transfer after IVF based on culture media concentrations of sHLA-G > or = 2 U/ml and good morphologic grade, a 65% pregnancy rate compared with a 0% pregnancy rate in those with <2 U/ml sHLA-G.


CONCLUSIONS
HLA-G is important for successful implantation in human beings. The HLA-G -725 promoter polymorphism is a risk factor for recurrent miscarriage. Measurement of sHLA-G in embryo culture media can help select embryos for transfer after IVF allowing fewer embryos to be transferred in an attempt to lower multiple gestation rates.
Roussev
Roumen G
RG
Millenova Immunology Laboratories, Chicago, IL, USA. rgroussev@yahoo.com
Coulam
Carolyn B
CB
D010064:Embryo Implantation; D005260:Female; D006680:HLA Antigens / Q000378:metabolism*; D059951:HLA-G Antigens; D015395:Histocompatibility Antigens Class I / Q000378:metabolism*; D006801:Humans; D011247:Pregnancy; D018873:Pregnancy Rate
D006680:HLA Antigens; D059951:HLA-G Antigens; D015395:Histocompatibility Antigens Class I