at Distant Areas of the Skin

This study has examined the systemic effects of a circulat-ing gene product, human interleukin 10 (IL-10), released from transduced keratinocytes. IL-10 is an anti-inflamma-tory cytokine which has an inhibitory effect on contact hy-persensitivity (CHS). An expression vector (phIL-10) was constructed for human IL-10 and was injected into the dor-sal skin of hairless rats. Local expression of IL-10 mRNA and protein was detected by reverse-transcriptase poly-merase chain reaction and immunohistochemical staining, respectively. Enzyme-linked immunosorbent assay showed that the amount of IL-10 in the local keratinocytes and in the circulation increased with the dose of phIL-10 trans-ferred. To determine whether circulating IL-10 could inhibit the effector phase of CHS at a distant area of the skin, vari-ous doses of phIL-10 were injected into the dorsal skin of sensitized rats before challenge on the ears. Our results showed that the degree of swelling of the ears of phIL-10– treated rats was significantly lower than that in the negative control animals. These results suggest that IL-10 released from transduced keratinocytes can enter the bloodstream and cause biological effects at distant areas of the skin. This study demonstrates that it may be possible to treat systemic disease using keratinocyte gene therapy.