[The skin--an immunocompetent organ]

Not only is the skin a mechanical barrier vis-à-vis the external environment, it also forms part of the immunological defence system. This skin-related component of the immune system is made up of a multitude of cells, and structures such as the Langerhans cells, keratinocytes, T-lymphocytes, endothelial cells, tissue macrophages, dendritic cells and mast cells. The skin is also provided with a dense network of afferent lymphatic vessels. Taking allergic contact dermatitis as an example, an immune response in the skin is described.