Figure 1.

Structure of the epidermis. The epidermal KCs are categorized into four layers, namely, the stratum basale, stratum spinosum, stratum granulosum (SG), and stratum corneum (SC). A functional epidermal barrier depends on the existence of the SC and tight junctions (TJs) formed in the SG. LCs can link with KCs to form TJs. In steady state (left), LC dendrites lie beneath the TJs. Upon activation (right), LCs elongate their dendrites to penetrate the KC TJs by forming tricellulin-dependent TJs between KC-LC-KC. The elongated dendrites are able to reach beneath the SC and take up Ag from the extra-TJ environment without destroying barrier integrity. The original figure was published in [7].