DIETARY SUPPLEMENTATION WITH VERY LONG-CHAIN N-3 FATTY-ACIDS IN MAN DECREASES EXPRESSION OF THE INTERLEUKIN-2 RECEPTOR (CD25) ON MITOGEN-STIMULATED LYMPHOCYTES FROM PATIENTS WITH INFLAMMATORY SKIN DISEASES

T-cell activation and cytokine production play an important role in several chronic inflammatory diseases. Because n-3 fatty acids exert beneficial effects on the clinical state of some of these diseases, we examined the effect of dietary supplementation of n-3 fatty acids on T-cell proliferation, expression of CD25 (interleukin-2 receptor alpha-chain), secretion of interleukin-2, interleukin-6 and tumour necrosis factor from T-cells from patients with psoriasis and atopic dermatitis. During 4 months, 21 patients supplied 6 g of highly concentrated ethyl esters of EPA and DHA in gelatin capsules daily to their diet. In the control group 20 patients supplied 6 g per day of corn oil in gelatin capsules to their diet. Eicosapentaenoic acid (20:5, n-3) of serum phospholipids increased from 14 (min 4-max 42) to 81 (min 59-max 144) mg l(-1) (P < 0.01) in patients with atopic dermatitis receiving n-3 fatty acids, and from 25 (min 7-max 66) to 74 (min 46-max 142) mg l(-1) (P < 0.01) in patients with psoriasis, whereas docosahexaenoic acid (22:6, n-3) increased from 65 (min 46-max 120) to 92 (min 54-max 121) mg l(-1) (P < 0.05) and from 81 (min 38-max 122) to 92 (min 63-max 169) mg l(-1) (NS) in atopic and psoriatic patients, respectively. The changes in the serum phospholipid fatty acid profile in the groups receiving n-3 fatty acids, correlate to the dietary intake of corresponding fatty acids. There was no significant change in the fatty acid pattern of serum phospholipids in the corn oil group before and after supplementation. Mitogen-induced secretion of interleukin-6 was significantly higher in patients with psoriasis compared to patients with atopic dermatitis, whereas the secretion of interleukin-2, tumour necrosis factor, PHA-induced T-cell proliferation and expression of CD25 on lymphocytes were similar in the two groups of patients. Patients receiving supplementation of n-3 fatty acids decreased significantly the percentage of CD25 positive lymphocytes from 40.5 before start to 35.5 (P < 0.05) after the trial. The patients who received corn oil increased the level of tumour necrosis factor from 10.95 pg ml(-1) before start to 1536 pg ml(-1) after the trial (P < 0.05). In conclusion, dietary intake of very long-chain n-3 fatty acids may suppress the expression of CD25 positive lymphocytes, which may partly account for the anti-inflammatory effect exerted by these fatty acids.