Discovery Could Boost Type 1 Diabetes Care

Researchers spot key player in success of transplanted insulin-producing cells

TUESDAY, Sept. 27, 2005 (HealthDay News) -- The survival of transplanted insulin-producing cells is improved when activation of "natural killer T" immune cells is blocked, Japanese researchers report.

They believe the finding could help boost the effectiveness of islet cell transplants for the treatment of insulin-dependent type 1 diabetes. This form of the disease (affecting about 5 percent of diabetics) is caused by the destruction of insulin-producing cells in the pancreas by the body's own immune T-cells.

Transplantation of these "islet cells" into the pancreas is a relatively new method of restoring insulin production. However, this treatment requires that the patient continue lifelong immunosuppression therapy, aimed at keeping immune responses at bay. Even with immunosuppression treatment, up to half the transplanted islet cells are quickly destroyed by the patient's own T-cells, however.

In their research with mice, the Japanese team showed that natural killer T (NTK) cells instigate this rapid destruction of transplanted islet cells. When the NKT cells become activated -- most likely in response to the stress of the transplant procedure -- they produce an inflammatory molecule called interferon (IFN)-gamma.

It's this molecule that helps activate immune T-cells to destroy islet cells, the researchers report in the Oct. 3 issue of the Journal of Experimental Medicine.

Transplanted islet cells survived in mice that lacked NKT cells or were unable to produce IFN-gamma, the researchers found. They also found that multiple doses of the drug alpha-galactosylceramide caused NKT cells to produce less IFN-gamma. Decreased production of IFN-gamma greatly improved the survival of transplanted islet cells, the study found.

According to the Japanese team, multiple doses of the drug -- currently in human clinical trials -- may help prevent the early loss of transplanted islet cells in humans.

More information

The American Diabetes Association has more about islet cell transplantation.

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