Overexpression of monocyte-derived cytokines in active psoriasis: a relation to coexistent arthropathy

An overexpression of inflammatory cytokines has been found in the lesional skin as well as peripheral blood in patients with psoriasis, although its etiological significance is not yet understood. In order to evaluate the cell type responsible for the elevated cytokines in the peripheral blood, we investigated cytokine profiles of the fractionated peripheral blood mononuclear cells (PBMCs) in 30 patients with psoriasis and 27 healthy controls. Without stimulation, higher levels of interleukin (IL)-1beta, IL-6, and IL-8 were produced by freshly isolated PBMCs from the patients than those from the controls. In the fractionated PBMCs, the monocyte-rich fractions were mainly responsible for the production of these cytokines and mRNA. The elevated levels of monocyte-derived cytokine mRNAs decreased following successful treatment with cyclosporin A. Although no correlation was found between the cytokine levels and the psoriasis area and severity index (PASI) scores, patients with arthropathy showed significantly high production levels of IL-1beta, IL-6, and IL-8. These findings suggest that monocytes are the major cell source producing inflammatory cytokines in the peripheral blood of psoriasis, and the increased cytokine levels are related to the coexistent arthropathy rather than the severity of cutaneous lesions.