Human keratinocyte induction of rapid effector function in antigen-specific memory CD4<sup>+</sup>and CD8<sup>+</sup>T cells
Black APB., Ardern-Jones MR., Kasprowicz V., Bowness P., Jones L., Bailey AS., Ogg GS.
The ability of human keratinocytes to present antigen to T cells is controversial and, indeed, it has been suggested that keratinocytes may promote T cell hyporesponsiveness. Furthermore, it is unclear whether keratinocytes can process antigen prior to MHC class I and class II presentation. We tested the ability of keratinocytes to induce functional responses in epitope-specific CD4+and CD8+memory T cells using peptides, protein and recombinant expression vectors as sources of antigen. Keratinocytes were able to efficiently process and present protein antigen to CD4+T cells, resulting in cytokine secretion (Th1 and Th2). This interaction was dependent on keratinocyte expression of HLA class II and ICAM-1, which could be induced by IFN-γ. In addition, keratinocytes could present virally encoded or exogenous peptide to CD8+T cells, resulting in T cell cytokine production and target cell lysis. Finally, T cell lines grown using keratinocytes as stimulators showed no loss of function. These findings demonstrate that keratinocytes are able to efficiently process and present antigen to CD4+and CD8+memory T cells and induce functional responses. The findings have broad implications for the pathogenesis of cutaneous disease and for transcutaneous drug or vaccine delivery. © 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.