Figure 7.

Proposed mechanism for mode of action of shikonin in skin tissues. Topical pretreatment with shikonin enhances the recruitment of DCs and other responsive immune cells via induction of RANTES, and in turn, increases the trafficking and population of these immune cells at a specific vaccination site. The increased number of immune cells accumulated at the vaccination site then increases the frequency of exposure or transfection of cells after subsequent DNA-based vaccination. The gene-based vaccines can further provide strong stimuli, due to the gene transfection process or the composition of the DNA vaccines (e.g., CpG), to activate skin DCs with transgenic antigenic signals to migrate to the draining lymph nodes where naïve T cells may be primed.