The role of Langerhans cells and keratinocytes in epidermal immunity

The immunology of the epidermis has received considerable study over recent years. After the antigen-presenting capacity of epidermal Langerhans cells was confirmed, subsequent studies suggested that keratinocytes could modulate certain immunologic events through production of a cytokine, epidermal cell-derived thymocyte-activating factor (ETAF). Most recently, a murine epidermal cell population, the dendritic Thy-1-positive cell, has been shown to possess natural killer-cell-like activity. In this review, the biology of these cell types are discussed. A discussion of allergic contact hypersensitivity and its alteration by ultraviolet light is used to illustrate some of the complex control mechanisms that continue to be the subject of ongoing study.