Nutrition and allorejection impact of lipids

Polyene n-3 and n-6 fatty acids are claimed to have immunomodulating properties. The impact of nutritional variations on transplant rejection was therefore studied in the heterotopic rat heart allotransplant model with particular focus on lipids. Twenty per cent fat emulsions with differing n-3/n-6 fatty acid ratios were continuously infused (9 g fat per kg bodyweight per day; n = 10 in each group) after transplantation until rejection: safflower oil (n-3/n-6 = 1/370), fish oil (7.6/1), soybean oil (1/6.5) and a 1:1 mixture of safflower and fish oil (1/2.1; oil control group). Graft survival time, subpopulations of infiltrating and circulating immunocompetent cells and interleukin-6 release by circulating mononuclear cells were analysed. In the safflower oil, fish oil and soybean oil groups graft survival was prolonged to 13.3, 12.3 and 10.4 days vs. 6.7 days in the oil control group and 7.8 days in the saline control group (p < 0.01). In the two groups with the highest prolongation of graft survival the number of infiltrating cells was reduced by up to 50% and the peripheral blood mononuclear cell interleukin-6 release by up to 45%. Beyond that, circulating T-cells were reduced in the fish oil group. The n-3/n-6 fatty acid ratio determines the immunomodulating effect of lipids. Both n-6 and n-3 fatty acids, if applied as the main fatty acid source, exert immunosuppressive effects by diminished infiltration, mobilization and cytokine release by immunocompetent cells. A n-3/n-6 fatty acid ratio of 1/2 proved to be immunologically neutral. The recipient's disposition to reject an allotransplant is influenced by the fatty acid composition of exogenously supplied lipids.