DIETARY FISH-OIL DIMINISHES THE ANTIGEN PRESENTATION ACTIVITY OF RAT DENDRITIC CELLS

Rats were fed for 6 weeks on a low fat (LF) diet or on high fat diets containing safflower oil [SO; rich in n-6 polyunsaturated fatty acids (PUFAs)] or fish oil (FO; rich in n-3 PUFAs), Lymph-borne dendritic ce lls (L-DC) were isolated after cannulation of the thoracic duct and we re used as antigen [keyhole limpet hemocyanin (KLH)] -presenting cells in an ex vivo assay that used KLH-sensitized spleen lymphocytes as th e responder cells, FO feeding significantly diminished the antigen pre sentation activity of L-DC compared with L-DC from rats fed each of th e other diets, The antigen presentation activity of L-DC from rats fed the SO diet was greater than that of L-DC from rats fed the LF diet, Feeding the FO diet significantly reduced both the proportion of CD2-p ositive L-DC and the level of CD2 expression on L-IDC compared with fe eding each of the other diets; the proportions of L-DC staining positi ve for CD40, CD18, CD54, CD11a, and MHC II were unaffected by diet, Ho wever, FO feeding reduced the level of expression of CD18, CD11a, MHC II, and CD54 on L-DC compared with feeding the other two diets; the le vel of expression of CD40 was unaffected by diet, This is the first st udy to report effects of dietary fatty acids on dendritic cells. The s uppressive effect of FO feeding may account for some of the beneficial effects of n-3 polyunsaturated fatty acids observed in clinical setti ngs, suck as prolonged survival of grafts and diminished chronic infla mmatory responses, However, such an effect may also be detrimental bec ause host defense toward bacterial and other antigens could be comprom ised.