Immune regulation in premalignant vulvar and vaginal disorders

During embryogenesis, the external genitalia develop under the influence of hormones. The vulva originates from the genital tubercle (clitoris), urogenital groove (vestibulum), urethral folds (labia minora) and genital swellings (labia majora). Structures belonging to the vulva are the mons pubis, labia majora and minora, the vestibule of the vagina, the hymen, the clitoris and the external urethral orifice. The outer aspects of the vulva are covered with normal cornified skin epithelium, which consists of three layers; the epidermis, dermis and subcutis. The epidermis of labia majora, labia minora and the frenulum of the clitoris is cornified stratified squamous epithelium and is developed from the embryonic ectoderm. It is histologically made up of four layers: the stratum germinativum or basal layer that forms the boundary with the dermis, the stratum spinosum, the stratum granulosum, and the stratum corneum (Fig. 1). The vestibule is lined with mucosal epithelium of endodermal origin, as is the vagina. The vaginal epithelium, however, is derived from the embryonic mesoderm.The transition of cornified epithelium to non-cornified mucous epithelium can be seen in some patients as the Hart’s line. The skin functions as a barrier to protect women from harmful external influences, which is particularly important in the genital area because of exposure to a wide range of bacteria, fungi and viruses. Cells that reside in the skin are keratinocytes, melanocytes, Merkel cells and Langerhans cells (LCs).The latter is an important resident of the epidermis; it is a bone marrow-derived dendritic cell which plays an essential role in the immune surveillance of the skin.5 The role of the immune system is to protect us from potential dangerous microorganisms such as viruses and bacteria. The immune response is a complex interaction between cells, cytokines, chemokines and other soluble proteins. All these players have their own specific role, which is essential for an effective defense against infection.

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