A longitudinal study of plasma n-3 fatty acid levels in a family with X-linked retinitis pigmentosa.

latter were prepared using defatted BSA, according to Mahoney et al. [ 111. After 48 h, (6-3H]thymidine (0.2 pCi/ well) was added to each well and the cells incubated for a further 18 h. The cells were harvested on to glass-fibre discs, which were washed and dried before measurement of radioactivity. The maximal [ ’Hlthymidine incorporation obtained in the presence of LPS was 14.9 f 2.5% (mean k S.E.M. from four separate cell preparations) of that obtained in the presence of Con A. The results of the effect of fatty acids upon LPSstimulated lymphocyte proliferation are shown in Table 1. The effect of fatty acids on Con A-stimulated lymphocyte proliferation are shown for comparison. B lymphocyte proliferation was inhibited by all fatty acids except 14:O; the greatest inhibition was caused by 20:4, n 6 , 18:2, n-6, 2 0 : 5 , n 3 and 22:6 , ti-3, and the least inhibition was caused by 14:O and 16:O. The two fish-oil-derived fatty acids tested caused similar degrees of inhibition and both were significantly less inhibitory than 20:4, n 6. These results indicate that a wide range of fatty acids are capable of inhibiting B lymphocyte proliferation in vitro. It must be noted, however, that all fatty acids, except 14:0, caused significantly less inhibition of B lymphocyte proliferation than that of T lymphocyte proliferation (Table 1 ), indicating that B lymphocytes are less susceptible to the inhibitory effects of fatty acids. This may result from differing abilities of the two cell types to incorporate or metabolize exogenously supplied fatty acids. Whatever the basis of the different susceptibilities of T and B cells, it is clear that fatty acids in general have an immunosuppressive effect but that the effect is greatest with polyunsaturated fatty acids. It is possible that the fatty acid-induced inhibition o f lymphocyte proliferation is due to modification of the fatty acid composition of membrane phospholipids, which could alter fluidity of the membrane. Such changes could effect many properties such as membrane potential, affinity of receptors or signal transduction. Whatever the mechanism involved, these results suggest that proliferation of both T and B lymphocytes, and hence an immune response, could be altered by dietary lipid manipulation.