Langerhans histiocytes, skin, S-100 immunoperoxidase stain
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Langerhans cells are easily identified by the S100 stain in normal skin. All immunoperoxidase stains will stain the cell of interest brown, so where-ever you see brown in this slide, there is a Langerhans histiocyte. The cells are simply monocyte/macrophages that do not migrate. In other words, they are tissue histiocytes. Like all other cells of monocyte/macrophage linage, their major function is to present antigens to T cells.