The interaction of vitamin E and polyunsaturated fatty acids (PUFA) affecting several disease states has been demonstrated. The mechanism of this interaction has been the subject of several different hypotheses. We wish to gather evidence to aid in the selection of the correct mechanism to explain the interaction. By dietary and in vitro control of the lipids available to the animals and their cells and tissues, we will investigate this interaction on three diverse biological systems: The immune system, platelets, and the gastrointestinal tract. These systems were chosen not only because we have had experience with them, but because they all have been shown to be affected by the presence or absence of vitamin E. We will therefore look at the dietary and in vitro effect of vitamin E, vitamin E analogs and PUFA on the following properties of the designated systems: 1. Immune system: the ability of lymphocytes to respond to mitogenic and antigenic stimuli as well as to interact with other cells of the immune system. 2. Platelets: the ability to aggregate and the effect on membrane properties as measured by changes in membrane potential, fluidity and platelet release. 3. Small bowel mucosa: membrane linked functions such as uptake of small molecules, membrane-linked enzymes, and morphology. It is hoped that if these measurements are made on several organ systems of animals fed diets varying in PUFA and vitamin E, some indication of the mechanism of interaction at the membrane level can be made.