Dietary fatty acid modulation of murine T-cell responses in vivo.

The effect of dietary fat concentration and saturation on T-cell functions in vivo were investigated by using delayed-type hypersensitivity (DTH) and graft-versus-host (GVH) reactions. These were selected because they circumvent the problem of fatty acid flux from the lymphocyte during in vitro assays. The DTH reaction to allogeneic line B16-BL6 melanoma cells was suppressed in BALB/c mice fed a diet containing 20% saturated fat (coconut oil) or polyunsaturated fat (safflower oil) compared to control mice fed a diet with the minimum of essential fatty acids (EFA). Likewise, DTH responsiveness of mice fed an EFA-deficient diet was less than that of mice fed the EFA control diet. The GVH reaction of C57BL/6 spleen cells injected into irradiated BALB/c mice was suppressed in those fed 20% polyunsaturated fat. Serum levels of linoleic acid increased commensurate with the levels of polyunsaturated fat in the diet. Likewise, previous work has demonstrated that levels of linoleic acid in whole lymphocytes changed in direct relation to the levels of fatty acids in serum and the diet. Thus, T-cell functions in vivo may be differentially affected by the degree of saturation or the concentration of dietary fat. Moreover, linoleic acid appears to play a pivotal role in modulating cellular immune responses.