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Leukemia accepted article preview online, 20 November 2017. doi:10.1038/leu.2017.335. ispartof: Leukemia issue:1 pages:1-7 ispartof: location:England status: published

Human leukocyte antigen G (HLA-G) is a tolerogenic molecule that acts on cells of both innate and adaptive immunity. This molecule has been associated with tumor progression, transplantation, placentation as well as the protection of the allogeneic fetus from the maternal immune system. We investigated HLA-G mRNA and protein expression in undifferentiated human embryonic stem cells (hESC) derived from the inner cell mass (ICM) of blastocysts. HESC self-renew indefinitely in culture while maintaining the potential to differentiate into all cell types of the body, providing an unlimited source of cells for therapy. HLA-G mRNA was found in three early and late passage hESC, as assessed by real time RT-PCR. Qualitative RT-PCR showed a different isoform expression pattern, although HLA-G1 mRNA was found in all three lines. Protein expression was demonstrated by immunocytochemistry and confirmed by flow cytometry and ELISA on a hESC extract. Binding of HLA-G with its ILT2 receptor demonstrated the functional active status. In order to verify this finding in a physiologically relevant setting, HLA-G protein expression was investigated during preimplantation development. We demonstrated HLA-G protein expression in blastocysts were we find it in trophectoderm (TE) but also in ICM cells. Co-expression of HLA-G and NANOG, which is known to be expressed in some nuclei of blastocyst ICM cells, confirmed these cells to be ICM cells. During blastocyst development, a down-regulation of HLA-G in the ICM cells was present. This data might be important for cell therapy and transplantation since undifferentiated hESC can contaminate the transplant of differentiated stem cells and develop into malignant cancer cells.

BACKGROUND: There have been concerns about validity and accuracy of the measurement of sHLA-G in embryo culture supernatants. In this systematic review, we quantified the diagnostic accuracy of sHLA-G for predicting the ability to achieve clinical pregnancy in women who are undergoing infertility treatment. METHODS: Medline and Embase were searched up to 7 September 2007, for full English and non-English articles concerning cohort studies evaluating sHLA-G in embryo culture for predicting clinical pregnancy in women undergoing IVF and ICSI. RESULTS: Eleven studies including 1813 patients met our inclusion criteria. In the individual studies, sensitivity ranged from 0.01 to 0.97, specificity from 0.18 to 0.98, the positive likelihood ratio from 0.34 to 3.21 and the negative likelihood ratio from 0.08 to 1.01. These values were highly heterogeneous with, in each case, I(2) values of >75%, and P-values for the Q statistic of CONCLUSIONS: Further research is needed with single-embryo culture, single-embryo transfer and highly sensitive detection techniques to determine the potential application of measuring sHLA-G in culture supernatant.

Successful implantation in the human is dependent on the early embryo avoiding immune recognition and destruction by the maternal immune system. Human leukocyte antigen G (HLAG), a non-classicalHLA class I antigen, is thought to play a key role in this by modulating cytokine secretion in order to control trophoblast invasion and to maintain a local immunotolerance. HLA-G is secreted in culture medium of cleavage stage IVF embryos but later on in development it is predominantly expressed in the invasive extravillous trophoblast of the placenta and in hematopoietic precursors originated from the extraembryonic yolk sac rather than in the fetus. We investigated the expression of HLA-G1/G5 in human embryonic stem cell lines (hESC) and throughout human preimplantation development by immunocytochemistry with the monoclonal MEM-G/9 antibody, in order to determine the upand down-regulation of HLA-G1/G5 in the early embryo. We detected expression of HLA-G1/G5 in nearly all oocytes, zygotes, cleavage stage and compacting embryos. At the blastocyst stage, the first stage at which differentiation into trophectoderm (TE) and inner cell mass (ICM) is detectable, HLA-G1/G5 protein was observed in the TE as well as in all the cells of the ICM. When the blastocyst started to hatch, the TE and the outer cells of the ICM remained positive whereas the staining in the inner cells of the ICM disappeared. Because hESC are undifferentiated pluripotent cells derived from the ICM of blastocysts, we examined six hESC lines. They all stained positive for HLA-G1/G5. We can conclude that HLAG1/ G5 is expressed in unfertilized oocytes and throughout preimplantation development. Since HLA-G1/G5 is expressed by hESC but not by epiblast cells (inner cells of the differentiated ICM), we hypothesize that hESC are derived from earlier undifferentiated ICM cells co-expressing stemness factors and HLA-G1/G5.

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The internal transcribed spacer (ITS1) region and the 5¢ part of the 5.8S ribosomal RNA gene of the ribosomal DNA repeat from 20 Toxoplasma gondii isolates was sequenced and found to be identical in all isolates, independent of host origin or virulence to mice. The ITS1 region from the closely related coccidian parasite Neospora caninum differed in 22% of its nucleotides. Hence, the ITS1 region provides a good marker for the distinction of T. gondii and N. caninum but is not useful for epidemiology studies of T. gondii.