Characterization and regulation of Skn-directed autoimmune skin lesions.

摘要

In the Skn model of autoimmunity, pathogenic T cells sensitized to Skn epidermal antigens (Skn-immune spleen cells or SIS cells) elicited disease in the form of skin lesions when adoptively transferred into shaved immuno-incompetent syngeneic adult recipients (‘lesion-forming animals’) while concomitant injection of immunoregulatory normal spleen cells at twice the concentration (2 x normal spleen cells or 2XNS cells) of SIS cells significantly lessened lesion development (‘lesion-controlling animals’) by Day 7 post cell transfer. In a time-course RT-PCR cytokine analysis of skin from lesion-forming and lesion-controlling animals, IL-7 mRNA was significantly elevated in lesion-controlling skin on Day 7 while no significant differences were observed for IL-2, IL-4, IL-10, IL-12, IFN-γ or TGF-β. The CD4+ T cell was identified as the immunoregulatory cells within the normal spleen cell population which, when adoptively transferred, significantly reduced lesion grade by Day 7 and were also associated with an elevated IL-7 mRNA level in the skin. To determine whether IL-7 expression without cell cotransfer could control skin lesion development, IL-7 was exogenously expressed in the skin of lesion-forming animals using a topically-applied plasmid-IL-7 somatic gene therapy. Daily application of plasmid-IL-7 facilitated by brushing at sites that flanked the known reactive site for lesion development significantly reduced lesion severity which was observed to be comparable to that observed with cotransfer of 2XNS or CD4-enriched normal spleen cells. The absence of endogenous IL-7 mRNA in lesion-controlling plasmid-IL-7 recipients indicated that plasmid-IL-7 mediated lesion control independently of endogenous IL-7. Exogenous-IL-7 mRNA expression in the skin was associated with a downregulated expression of endogenous IL-7 messages suggesting that an IL-7 homeostatic mechanism existed in the skin responsive to plasmid-IL-7 therapy. Furthermore, plasmid-IL-7 mRNA expression in the skin did not appear to disrupt the cytokine milieu of the skin or to work in concert with other cytokines analyzed. While others have reported a regulatory role for CD4+ T cells, this represents the first report of a topically applied somatic gene delivery of IL-7 in the skin of mice resulting in the control of autoimmune skin lesions.