HLA-G differs from the other MHC class I genes by its low polymorphism and alternative splicing that generates seven HLA-G proteins, whose tissue-distribution is restricted to normal fetal and adult tissues that display a tolerogeneic function toward both innate and acquired immune cells. Soluble HLA-G is an immunosuppressive molecule inducing apoptosis of activated CD8(+) T cells and down-modulating CD4(+) T cell proliferation. Recently, using specific ELISA to analyse the presence of sHLA-G molecules in culture supernatants of early embryos obtained by in vitro fertilization (IVF) before transfer, several reports demonstrated that positive embryo implantations occurred with embryo secreting sHLA-G molecules. These breakthrough results indicate that sHLA-G ELISA can be a useful biochemical assay in addition to embryo morphology in embryo selection for transfer in IVF treatment if there are other embryos with the same morphology. Furthermore, monitoring of sHLA-G in amniotic fluid and plasma of pregnant women may have an important prognostic value to recognize pathological situations. Other interesting observations suggest that HLA-G molecules seem to be directly involved in transplant acceptation, and their analysis should be taken into consideration when monitoring transplant-patients status. In addition, soluble HLA-G plasma levels are increased in lyphoproliferative disorders or in patients suffering from malignant melanoma, glioma, breast and ovarian cancer.
- References to HLA-G (soluble HLA-G)