Lack of increase in granulocyte colony-stimulating factor in psoriatic skin

Previously, we showed an elevated level of pro-inflammatory cytokine granulocyte-macrophage colony-stimulating factor (GM-CSF) in psoriatic skin. Granulocyte (G)-CSF, which is also released from the infiltrating cells and epidermal keratinocytes, profoundly influences the biological activities of terminally differentiated neutrophils, in addition to its supporting effects on the proliferation and differentiation of progenitor cells of neutrophil lineage. We have carried out enzyme immunoassay for G-CSF in suction blister fluids and horny tissue extracts from psoriatic skin. Although some samples of the blister fluids and stratum corneum extracts showed G-CSF, there were no significant differences between the concentration in normal and psoriatic skin. These results suggest that, among CSFs, GM-CSF plays a more important role than G-CSF in the local immune responses in psoriasis.