[Identification of Langerhans cells in dermatology]

This paper describes our own findings on the role of Langerhans' cells in dermatology and discusses literature data on their detection in seven different dermatoses. The skin is an integral part of immune system. During the past 30 years, increasing evidence has been accumulated that the skin contains cellular elements which are needed for the initiation and expression of immune response. Langerhans' cells (LCs) are dendritic cells originating in the bone marrow. They reside mainly within stratified squamous epithelia and constitute approximately 2-4% of epithelial cells. LCs are epidermal antigen presenting cells which play a crucial role in allergic contact hypersensitivity, viral diseases, graft versus host disease and elimination of neo-plastic cell clones. They express antigens conjugated with major histocompatibility complex (MHC) class II positive molecules on their surfaces for presentation to T-helper lymphocytes. LCs cannot be identified in routinely prepared histologic testing but can be visualised at the light microscope level by histochemical and immunologic techniques. Appropriate methods for the detection of Langerhans' cells in dermatology (also shown by our own experience) are histoenzymatic methods of adenosintriphosphatase (ATP-ase), acid phosphatase (AP), alpha-naphthylacetatesterase (ANAE and peroxidase-antiperoxidase immunohistochemistry method with polyclonal S-100 protein antibody (PAP). LCs are the only cells in normal skin with ATP-ase activity. Histoenzymatic methods used in patients with atopic dermatitis, vitiligo, mycosis fungoides, Behcet's disease, lichen ruber planus, psoriasis vulgaris, irritant dermatitis and allergic contact dermatitis demonstrated LSs in epidermis and dermis. ANAE and AP showed concordance and were suitable histochemical markers for LC distribution and macrophages in the dermis in mycosis fungoides, atopic dermatitis, psoriasis vulgaris, irritant chronic dermatitis and Bechet's disease. Our experience of the human skin showed a strong activity of calcium-activated adenosine triphosphatase in LCs. LCs in the guinea pig skin can be demonstrated by Mg++ and Ca++ activated adenosine triphosphatase, but a stronger activity of Ca++ activated adenosine triphosphatase in LCs after irritation. Ca++ ATP-ase as an indicator of energy-dependent pump is the reflection of intracellular calcium level, which is a significant factor for regulating the growth and metabolism of the cells. LCs are found as target cells during the efferent phase of contact allergic reaction. Immunohistochemical methods, define the role of LCs in dermatology more precisely and allow complete immunologic recognition within the epidermis.