Skin-derived dendritic cells

This test uses an in vitro human dendritic cell culture to obtain information of the potential for various chemicals to induce allergic contact dermatitis. This test is used as an alternative to the Local Lymph node assay (LLNA) to minimize or replace the use of live animal testing for predicting skin sensitization (Kimber et al. 2002, see below). The test allows for evaluation of skin sensitization by examining the presence of cell surface markers on Periperal Blood Mononuclear Cell (PBMC)-derived dendritic cells (DC) that are known to be involved in the development of allergic contact dermatitis. 

Since the initial development of methods for in vitro cnlture of human keratinocytes (Rheinwald and Green, 1975), two-dimensional monolayer cultures of submerged keratinocytes have been widely utilized for skin-related research. Primary and immortalized fibroblast and melanocyte cultures are also now widely available for in vitro research and toxicology testing applications (Hsu and Herlyn, 1996 Costin and Hearing, 2007). Skin-resident immune cells (e.g., Langerhans cells) are difficult to isolate and maintain in primary culture. However, monocyte-derived dendritic cells and dendritic cells derived from cord blood precursors are well established, as are a variety of immortalized dendritic-like cell lines (Ayehunie et al., 2009 Reuter et al., 2011). 

Keratinocytes secrete a unique profile of chemo-kines and cytokines after exposure to proinflam-matory cytokines. Keratinocyte-derived thymic stromal lymphopoietin (TSLP) may be of particular importance in atopic dermatitis This protein is undetectable in normal skin or non-lesional skin in patients with atopic dermatitis, but is highly expressed in acute and chronic atopic dermatitis lesions [18]. TSLP instructs human dendritic cells to create a Th-2-permissive microenvironment by inducing the expression of OX40L which triggers the differentiation of inflammatory Th-2 cells [48]. 

Antigen-presenting cells (APCs) are a heterogeneous population of cells with extraordinary immunostimulatory capacity. Some play an important role in the induction of the function of T helper cells and some communicate with other lymphocytes. Cytokines can render the ability to present antigens to various cell types. This results in the expression of MHC class II molecules, which are sometimes lacking on some cells such as endothelial cells. The different types of APCs include macrophages, dendritic cells, B cells and interdigitating cells. APCs are mostly derived from bone marrow and are distributed in lymphoid tissues and in the skin. These three types of major APCs are also called professional APCs. 

Pablos, J. L., Amara, A., Bouloc, A., Santiago, B., Caruz, A., Galindo, M., Delaunay, T., Virelizier, J. L., and Arenzana-Seisdedos, F. (1999). Stromal-cell derived factor is expressed by dendritic cells and endothelium in human skin. Am. J. Pathol. 155, 1577-1586. 

Cornbleet melanin is produced by dendritic cells which are derived from the neural crest in the negro skin, these cells give a positive dopa oxidase reaction from the third month of fetal life. Subsequently the melanin is transferred to the cells of the Malpighian layer of the dermis. 

Nakamura, K., Williams, I. R., and Kupper, T. S. (1995) Keratinocyte-derived monocyte chemoattractant protein 1 (MCP-1) analysis in a transgenic model demonstrates MCP-1 can recruit dendritic and Langerhans cells to skin. J. Invest. Dermatol. 105, 635-643. 

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