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Amnion epithelial cells, in contrast to trophoblast cells, express all classical HLA class I molecules together with
A Hammer1, H Hutter, A Blaschitz
1Department of Histology and Embryology, Karl-Franzens-University, Graz, Austria.
Problem:
The expression of the non-classical HLA-G gene has been shown at the protein level on trophoblast-derived embryonic tissue, like the extravillous cytotrophoblast. However, the presence of HLA-G on embryoblast-derived cells is currently controversial. The amnion epithelium is an embryoblast-derived cell layer covering the amnion cavity and is the main source for the amnion fluid.
Method:
The expression of HLA class I molecules was investigated by immunohistochemical, biochemical, and molecular biological methods in amnion membranes and amnion fluid.
Results:
Immunohistochemically, HLA-C and occasionally also-B molecules as well as HLA-A and/or -G molecules have been identified on amnion epithelial cells. These results were extended by Western blotting with purified amnion epithelial cells where HLA-B and/or -C, HLA-A and HLA-G antigens have been detected. As expected HLA-G mRNA was detected in amino epithelial cells. Furthermore, classical HLA molecules as well as HLA-G were found in amnion fluid.
Conclusion:
These results show that the amnion epithelium frequently expresses classical HLA class I molecules as well as HLA-G. The expression of HLA-G antigens on amnion epithelial cells and their presence in the amnion fluid, which is continually ingested by the fetus, may be particularly relevant for the induction of peripheral tolerance.