The serum levels of several cytokines were determined in 94 patients with Adamantiades-Behçet's disease (ABD), aged 36.1+/-11.0 years, during the active stage (n = 75) and the inactive stage (n = 19) of the disease. A group of 75 healthy individuals matched for age and sex served as controls. Cytokine levels were determined using commercially available ELISA kits. Of the 75 patients with active disease and 19 with inactive disease, 38 (51%) and 4 (21%), respectively, and 23 healthy controls (31%) were found to have detectable levels of interleukin 8 (IL-8) in their serum (P < 0.05). Also, increased IL-8 serum levels were found in patients with active disease (median 12 pg/ml, P = 0.010) compared to patients with inactive disease (< or = 10 pg/ml) and to healthy controls (< or = 10 pg/ml). In particular, patients with oral aphthous ulcers (n = 51, 34 pg/ml) and neurological features (n = 4, 71 pg/ml) exhibited increased IL-8 levels. In contrast, there was no correlation between disease activity and the serum levels of IL-1alpha, IL-1beta, tumor necrosis factor alpha (TNF-alpha), soluble intercellular adhesion molecule-1 or basic fibroblast growth factor (bFGF). In a second set of experiments, the involvement of dermal microvascular endothelial cells in IL-8 secretion was investigated. Immortalized human dermal microvascular endothelial cells (HMEC-1 cells) were maintained for 4 h in vitro with serum from 18 ABD patients or with IL-1beta, a known stimulator of IL-8 synthesis, TNF-alpha or their combination at five- to tenfold higher concentrations than those found in the serum of ABD patients. Increased IL-8 secretion was found after incubation with ABD patients' serum (median 20 pg/ml), but IL-1beta, TNF-alpha and IL-1beta + TNF-alpha failed to induce IL-8 secretion by HMEC-1 cells (< or = 1-1.2 pg/ml) in biologically relevant concentrations. Our study showed increased IL-8 serum levels in ABD patients with active oral and neurological manifestations. Human microvascular endothelial cells may, at least partially, be responsible for the enhanced IL-8 secretion in the active stage of the disease.