sHLA-G production by human IVF embryos: can it be measured reliably?

A number of reports have demonstrated that sHLA-G can be detected in the culture medium of human IVF embryos and that levels correlate with the potential of an embryo to implant. This has aroused considerable interest in the IVF field. If sHLA-G can be used as a non-invasive marker of embryo quality, it will facilitate selection of the best embryos to transfer to the mother and thereby increase IVF pregnancy rates. However, there have been concerns about some aspects of these studies, including the sensitivity of the sHLA-G ELISAs used, the IVF culture conditions and the levels of sHLA-G which have been reported. A recent study by Sageshima et al. [J. Reprod. Immunol. 75, 11-22, 2007] attempts to address some of these concerns. However, despite using a sensitive ELISA, they were unable to detect sHLA-G in 111 embryo culture supernatants, or sHLA-G secretion by less than 10,000 sHLA-G transfected cells. They concluded that it is not possible to measure sHLA-G production by human embryos. This study has highlighted technical differences between IVF culture techniques and sHLA-G ELISAs that are currently confounding the system. Further collaboration between the research groups involved is required to establish robust reproducible systems that function identically in all laboratories.