Detection of inflammatory cytokines in psoriatic skin

Recent investigations have revealed the involvement of cytokines in the pathogenesis of psoriasis. This study examined the amount of inflammatory cytokines--interleukin-1 (IL-1), interleukin-6 (IL-6) and granulocyte macrophage colony-stimulating factor (GM-CSF)--released into the supernatants of organ cultures of involved and uninvolved skin from psoriatic patients and normal skin from healthy individuals. Bioassays were employed to detect the activities of IL-1 and IL-6. Enzyme-linked immunosorbent assay (ELISA) methods were used to quantitate immunoreactive IL-1 alpha, IL-1 beta, IL-6 and GM-CSF. The activity of IL-1 in uninvolved psoriatic skin was found to be increased relative to that in involved and normal skin, while immunoreactive IL-1 beta was found only in involved skin. A neutralization experiment showed that bioactive IL-1 was mostly attributable to IL-1 alpha. Uninvolved psoriatic skin also secreted higher amounts of both bioactive and immunoreactive IL-6 compared with involved skin. Immunoreactive GM-CSF was detected in uninvolved skin only. These cytokines detected in uninvolved skin may have been released from epidermal or mesenchymal cells, since uninvolved skin contained fewer inflammatory infiltrates. Our results offer additional evidence that increased amounts of inflammatory cytokines in uninvolved skin may provide a preliminary condition and play important roles in the initial events in the evolution of psoriatic lesions.