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Dynamics of Langerhans cells in genetically defined murine epidermal cell culture

Unlike keratinocytes, Langerhans cells express both surface ATPase activity and Ia (HLA‐DR) ANTIGENS. A well‐characterized in vitro system containing Langerhans cells would be of great use in elucidating their functions. Thus, epidermal cell cultures derived from neonatal Balb/c mice were examined for the presence of Langerhans cells. Twenty‐four hours after initiation of culture, ATPase‐ and Ia‐positive cells were seen to be associated with cell aggregates. By day 3, Langerhans cells migrated on to the substratum and, as the cultures matured and stratified, were seen both in groups and as single cells for the duration of the cultures (day 14). During culture, although the total number of cells increased, the percentage of cells expressing Ia antigen and ATPase activity remained constant, suggesting that Langerhans cells increase in number during cell culture. Such a situation could arise from actual division of Langerhans cells during culture or from latent expression of Ia antigen and ATPase activity by pre‐existing cells. This is the first study of the dynamics of Langerhans cells in a cell culture system and shows that Langerhans cells are present throughout the lifespan of the cultures.