Dr. Jekyll and Mr. Hyde - Distinctiveness and plasticity of mononuclear phagocytes in the mouse skin

textabstractAntigen-presenting cells are crucial participants in the defense of the body against potentially pathogenic invaders. In an immature state, they reside in all peripheral sites, where they can recognize and take up antigens. Once they have encountered antigens, they may become activated. As a consequence, they will migrate to draining lymph nodes, where they can activate naïve T cells to become the main effector cells of the immune system. These T cells can then migrate back to the affected site to help to rid the body of the invaders. The skin, as the largest organ of the body, contains many cells that have the potential to develop into effective antigen-presenting cells (discussed in Chapters 1 and 2). The epidermis, the outermost layer, has its population of Langerhans cells. These cells form a tight network with connecting cellular protrusions. Via these, they sample endogenous as well as exogenous molecules that get into contact with the epidermis. As these cells have been known now for quite a while, their functions in the epidemis as well as after migration into skin-draining lymph nodes have been extensively studied. The dermis, the second layer of the skin, also contains cells with potential antigenpresenting capacity. These cells are, in contrast to the epidermal Langerhans cells, much less well investigated. The aim of this thesis study, outlined in Chapter 3, therefore was to analyze the antigen-presenting cells of the mouse dermis in more detail and to compare them to the epidermis-derived Langerhans cells