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Figure 1: Skin exposure to allergens induces maturation of LCs and migration to regional lymph nodes. After disrupture of the epidermal barrier, haptens such chemicals gain access to the deeper compartment of the skin. Even in steady state, sentinels of the immune system, LCs, move their protrusions between the keratinocytes to the tip of the inner cornified cell layer to sample antigens. If an allergen is detected in the context of danger, the antigen-loaded LC leaves the epidermis and migrates to the lymph node where cytotoxic T cells and T helper cells are stimulated to proliferate and acquire a specific phenotype. After skin inflammation, LCs are recruited from blood monocytes and repopulate the epidermis. DC, dendritic cell; LC, Langerhans cell; MHC, major histocompatibility complex; TCR, T cell receptor.