Effect of high/low dietary linoleic acid levels on the function and fatty acid composition of T-lymphocytes of normal and diabetic rats.

T-lymphocytes play a central role in the initiation, regulation and effector functions of immune responses. Changes in membrane composition can alter the membrane fluidity, receptor distribution and consequently function of these cells. Altered immune response in the diabetic state may be attributed partly to diabetes induced alterations in the metabolism of essential fatty acids. We have investigated the effect of dietary linoleic acid on T cell membrane composition and T cell mediated immune responses in normal and diabetic rats. Streptozotocin induced diabetes was found to produce lower T cell proliferative responses in mixed lymphocyte reactions and upon mitogen stimulation. Feeding of a diet rich in linoleic acid did not improve these responses. Feeding a diet low in linoleic acid further lowered the T cell dependent immune responses. We also found lower levels of 18:2 omega 6 fatty acids in the membrane phospholipids of these T cells. Levels of 20:4 omega 6 fatty acids were altered as a result of diabetes and diet composition. These fatty acids are the precursors of prostaglandins which are known to influence immune responses. It is concluded that diabetes results in significant alterations in T cell membrane composition and function in a manner that can be manipulated by modifications of the fatty acid composition of the diet. The present study suggests that diet fat modification may be important in regulating T cell-mediated immunity in insulin dependent diabetes mellitus.