Isolation of human skin dendritic cells by in vitro migration

In the human skin, various types of antigen-presenting cells (APC) are present. In the epidermis, they are identified ultrastructurally as Langerhans cells (LC) by the presence of Birbeck granules. LC are considered to belong to the family of dendritic cells (DC) that are important for the initiation of immune responses (1). In the dermis, macrophages and DC are present (2,3). The expression of CD1a molecules can be used to identify DC in the skin (4,5), because macrophages do not express this marker. In vivo, these skin DC are supposed to take up antigens penetrating in the skin. Thereafter, they migrate via the afferent lymphatics into the draining lymph nodes, where a T-cell response can be initiated (6,7). During migration, the DC mature into potent APC. Besides an increase in MHC class II expression, adhesion (8,9) and B7 co-stimulatory molecules (10) are up-regulated. Most research on skin DC has been carried out with cells isolated from enzyme digested skin (8-10). In this chapter, we describe a method to obtain DC from human skin without enzymes, by making use of their migratory capacities. The cells migrate "spontaneously" out of the skin during culture. Characterization of the cells shows that mature DC are obtained with a marker expression not influenced by enzymes.