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Some 30 percent of Japanese may experience rejection after receiving transplants of cells developed from induced pluripotent stem (iPS) cells derived from someone other than the patient, a Japanese research team has found.

The team, including Hiroshi Kawamoto, professor at Kyoto University’s Institute for Frontier Life and Medical Sciences, also discovered that rejection can be prevented by modifying genes in the transplanted cells.

The research results will be published in the online edition of the U.S. journal Stem Cell Reports on Thursday.

“Although 30 percent is a figure that cannot be ignored, the problem will become trivial if the genes are modified and immunosuppressants are used,” Kawamoto said.

In iPS-cell-based regenerative medicine, most of the cells used are stocked in advance because acquiring an adequate amount from the actual patient costs time and money. Nevertheless, experts are aware that patients’ immune systems can reject iPS cells derived from other people.

Through experiments in test tubes, Kawamoto’s team found that rejection of cells made from other people’s iPS cells occurs mainly when the human leukocyte antigens (HLA), which play a critical role in immune reactions, don’t match that of the patient.

Based on the experiments, the team estimates that about 30 percent of Japanese experience rejection during iPS cell transplants.

The team managed to prevent rejection by introducing HLA genes matching the recipients’ types into iPS cells transplanted from other people.

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