Israeli Scientist: Stem Cells Recognizable by Immune System

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Last updated at: (Beijing Time) Wednesday, July 10, 2002

Israeli Scientist: Stem Cells Recognizable by Immune System

Israeli cell biologists found human embryonic stem (ES) cells got no free pass from the immune system, contrary to some researchers' early hopes.

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Israeli cell biologists found human embryonic stem (ES) cells got no free pass from the immune system, contrary to some researchers' early hopes.

A team led by Nissim Benvenisty of the Hebrew University of Jerusalem looked in human ES cell lines for MHC molecules, which help the immune system identify an invader.

The researchers measured MHC molecules during three stages of ES cell development using a fluorescent-tagged antibody. As a control, they also tested a non-ES human cell line called HeLa, Benvenisty said.

The scientists found very low, but consistent, expression of MHC class-1 molecules on the undifferentiated ES cells, as they describe in a paper published online the week of July eighth by the American Proceedings of the National Academy of Sciences.

Some earlier evidence from human embryos had showed that ES cells might be "immune privileged," unrecognizable by the body's defenses against foreign cells. One study reported that the embryocells that give rise to ES cells do not express the MHC proteins.

The new results laid to rest the hope that ES cells might remain under the radar of the immune system, said Hugh Auchincloss,a US transplant surgeon at Harvard Medical School in Boston.

But the news was not all bad. Relatively low levels of MHC expression might at least mean that tissues derived from ES cells would be less prone to rejection than today's whole-organ transplants, noted Andrew Bradley, a transplant surgeon at Cambridge University, U.K.

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