Leukotriene B4 in atopic dermatitis: increased skin levels and altered sensitivity of peripheral blood T-cells.

Employing a radioimmunoassay, de-proteinated suction blister fluid from 12 patients with active atopic dermatitis appeared to contain higher levels of the pro-inflammatory and immunomodulatory mediator leukotriene B4 (LTB4) than suction blister fluid from 12 non-atopic individuals. Indirect support for the identity of the mediator was obtained by HPLC of pooled samples. Nylon wool enriched T cells from six patients with atopic dermatitis and six non-atopic people preincubated with LTB4 (10(-10) M - 10(-8) M) expressed no statistically significant suppression in co-culture with mitogen stimulated autologous mononuclear cells, and there was no difference between atopic and non-atopic T cells in this respect. In contrast, LTB4 induced a dose-dependent reduction in the percentage of phenotypic Leu 2a (suppressor) cells leading to an increased helper/suppressor ratio in five atopic patients that was not observed in five non-atopics. Elevated skin levels of LTB4 may initiate or amplify dermal inflammation, and abnormal T cell response to the mediator may account for the increased helper/suppressor ratio characteristic of patients with atopic dermatitis.