INDUCTION OF IL-10 GENE-EXPRESSION IN HUMAN KERATINOCYTES BY UVB EXPOSURE IN-VIVO AND IN-VITRO

Numerous studies have demonstrated that ultraviolet B (UVB) irradiatio n has profound effects on the skin and systemic immune systems. Becaus e many of the effects of UVB result in suppression of contact sensitiv ity responses and because IL-10 induces a Th2 rather than a Th1 respon se, we sought to determine whether UVB irradiation induces IL-10 trans cription and subsequent protein secretion by human epidermal cells. Sk in of nine volunteers was exposed to UVB or sham irradiation, and epid ermal cell suspensions were prepared from suction blister roofs 24 h t hereafter. mRNA was extracted using oligo dT-coated magnetic beads, an d IL-10 cDNA was amplified with a sensitive RT-PCR technique. We found that IL-10 was constitutively expressed by epidermal cells in 5 of 9 volunteers and that IL-10 message was up-regulated by UVB exposure in all experiments. Since epidermis consists of a heterogeneous cell popu lation with distinct cytokine profiles, we determined whether UVB caus ed enhanced IL-10 transcription and protein secretion in human keratin ocyte cultures. In these experiments, IL-10 was constitutively express ed by keratinocytes and UVB up-regulated IL-10 gene expression in a do se-dependent manner 24 h after in vitro irradiation, coinciding with I L-10 protein secretion into the culture supernatants. Taken together, the findings indicate that UVB irradiation induces IL-10 in human kera tinocytes and suggest that keratinocyte-derived IL-10 may be an import ant component of the immunosuppression that results from UVB irradiati on.