Major actors of the adaptive immune response. The adaptive immune system mounts a stronger, antigen-specific immune response when the innate immune response fails to eliminate pathogens. The first phase consists of the activation of antigen-presenting cells such as DCs allowing their migration into lymph nodes where they prime naïve T cells. Activated T cells migrate back to the site of infection where they induce cell-mediated and humoral immunity causing mediator release by the immune cells present at the site of infection. The resulting cytokinic environment stimulates epidermal cells mainly KCs to release further mediators that activate and maintain the dermal immune response. Hence, a positive feedback loop forms. DCs: dendritic cells; KCs: keratinocytes; TH: T helper; MHC: major histocompatibility class; IFN: interferon; CD: cluster of differentiation; IL: interleukin; TNF: tumor necrosis factor.