BACKGROUND: Psoriatic plaques have been shown to contain increased levels of proinflammatory cytokines. Serum levels of interleukin (IL)-6, IL-7, IL-8, and interferon (IFN)-gamma have been reported elevated in psoriatic patients. AIM: To evaluate serum cytokine profiles in psoriasis patients by improved enzyme-linked immunosorbent assay (ELISA) technique and to correlate these levels with disease severity. METHODS: We analyzed single serum samples from 10 patients with active untreated psoriasis, two patients with active treated psoriasis, and five healthy volunteers for major T helper type 1 and T helper type 2 cytokines using the LINCOplex ELISA multi-analyte detection system that permits simultaneous detection of multiple cytokines from a single sample. The disease severity, including erythema, induration, scale, and surface area, was assessed. RESULTS: IFN-gamma was markedly elevated in all sera from psoriasis patients, 33.8 +/- 1.3 pg/ml (mean +/- standard error) versus 8 +/- 1.5 pg/ml for normal controls (p < 0.01), and positively correlated with all indices of disease severity (Spearman r > 0.6). IL-8 was also increased in psoriasis patients (24.4 +/- 1.8 pg/ml) versus normal controls (3.6 +/- 1.2 pg/ml) (p < 0.05) and positively correlated with the degree of erythema (Spearman r > 0.6). Mean IL-12 levels were decreased in sera from psoriasis patients (8.5 +/- 1.2 pg/ml) compared with normal controls (42.2 +/- 5.3 pg/ml) (p < 0.01). Also, serum IL-10 levels were below detection levels in psoriatics compared with controls (6.4 +/- 1.3 pg/ml). CONCLUSIONS: This new ELISA system allowed rapid and reliable detection of numerous cytokines in single serum samples from patients with psoriasis. We observed that IFN-gamma and IL-8 cytokines were elevated in psoriatics and correlated with parameters of disease severity while IL-10 and IL-12 were decreased.