Dieting away organ rejection, diseases.

Dieting away organ rejection, diseases

Removing essential fatty acids from the diet of organ-donating rats causes loss of immune cells from their tissues, thus providing a unique way to prevent a recipient's rejection fo the transplanted organ, scientists report. While the researchers agree that human donors are unlikely ever to use a similar diet, they say it is possible a drug may someday mimic the diet's rejection-suppressing effects. Data from the studies also suggest such an approach may help prevent auto-immune diseases as well as local inflammatory reactions -- without destroying the body's beneficial immune responses.

Last year, researchers at Washington University School of Medicine in St. Louis found that immune cells called lapositive macrophages disappear from the kidneys of rats fed a diet deficient in essential fatty acids, which the body does not make and which threfor must be supplied in the diet. The mechanism causing this depletion remains unknown. But because these cells are in part responsible for a transplanted organ being perceived as "foreign" by a recipient, George F. Schreiner and his co-workers then tested whether such a dietary treatment could help save transplanted rat kidney given to unrelated rats. They report in the May 20 SCIENCE that kidneys from rats fed the special diet for at least two months survived after being transplanted. Kidneys from normally fed rats, however, were quickly rejected.

Recipient rats remained on normal food throughout the study, and the fatty acid composition of their new kidneys returned to normal within five days after surgery. Macrophages also returned during the same period, but came from the recipient and therefore did not cause a rejection response.

Schreiner said in an interview the scientists are now focusing on a fatty acid called Mead acid, which accumulates in the specially fed anumals. He says Mead acid may be interfering with the movement of macrophages into tissues, and the scientists hope it or a similar compound can replace harsh immunosuppressive drugs now in use. Also of interest, Schreiner says, are yet-unpublished results showing rats are "markedly protected" against tissue-destroying inflammatory reactions. He says the diet also blocks diabetes in two rodent models, probably by stopping macrophage influx into pancreatic cells destroyed during diabetes. Although the treatment apparently prevents such autoimmune processes, the animals can still protect themselves against infection, he says.