FISH-OIL SUPPLEMENTATION INHIBITS THE EXPRESSION OF MAJOR HISTOCOMPATIBILITY COMPLEX CLASS-II MOLECULES AND ADHESION MOLECULES ON HUMAN MONOCYTES

To test the hypothesis that fish oil supplementation can inhibit the e xpression of functionally associated molecules on the surface of human blood monocytes, we randomly assigned 12 healthy adults to receive ei ther an n-3 polyunsaturated fatty acid-rich fish oil supplement for 21 d or to receive no supplement. The percentage of monocytes expressing major histocompatibility complex (MHC) class II molecules (HLA-DR, -D P, and -DQ), intercellular adhesion molecule-1, and leukocyte function -associated antigen-1, and the intensity of expression of each molecul e were quantified before and after the study period. Monocytes were ex amined immediately after blood sampling and again after incubation in serum-free culture medium for 24 h in the presence of interferon-gamma to up-regulate expression of MHC class II molecules by the monocytes. The intensity of expression of all the monocyte surface molecules exa mined was significantly reduced after fish oil supplementation (P < 0. 025), although there was no change in the percentage of monocytes expr essing each molecule. After incubation with interferon-gamma, there wa s a similar inhibition of surface molecule expression (with the except ion of HLA-DQ) by monocytes from the fish oil-supplemented group, and there was a reduction in the percentage of monocytes expressing both H LA-DR and -DP molecules (P < 0.025). No significant changes were obser ved in the reference group. Dietary supplementation with fish oil can inhibit the expression of surface molecules involved in the function o f human antigen-presenting cells, a potential mechanism by which n-3 f atty acids may suppress cell-mediated immune responses.