Info

aand, not determined; -, no expression; +/-, expression under certain conditions or in a subset of cells; +, low to moderate levels of expression; ++, moderate to high levels of expression. "Murine Langerhans cells have a similar antigenic profile. c Blood dendritic cells cultured over a 36-hour period as described by Steinman and coworkers.

aand, not determined; -, no expression; +/-, expression under certain conditions or in a subset of cells; +, low to moderate levels of expression; ++, moderate to high levels of expression. "Murine Langerhans cells have a similar antigenic profile. c Blood dendritic cells cultured over a 36-hour period as described by Steinman and coworkers.

derived cells. In general, I.angerhans cells in situ and freshly isolated I.angerhans cells represent functionally 'immature' dendritic cells. They express lower levels of cell surface MHC class II molecules and stimulate resting T cells less well in mixed lymphocyte reactions when compared to 'mature' dendritic cells, e.g. peripheral blood dendritic cells. However, upon culturing in vitro for 2-3 days, Lang-erhans cells upregulate MHC class II expression, as well as costimulatory molecules, and become functionally 'mature', i.e. they become potent stimulators in mixed lymphocyte reactions. Table 3 outlines the cell surface antigens expressed by both freshly isolated and cultured Langerhans cells, with a comparison to the antigenic profiles observed on blood dendritic cells and monocytes/macrophages. Of note, cell surface expression of CDla is a reliable marker for human Langerhans cells (Figure 2); the only other cells that express this MHC class I-like molecule include a subset of cortical thymocytes and a small subset of dermal dendritic cells.

Because of the difficulty in isolating large numbers of relatively pure cells, elucidation of the cytokines produced by Langerhans cells (as well as by other dendritic cells) has been difficult. In particular, the presence of small numbers of contaminating kera-tinocytes (which produce a wide array of cytokines and growth factors) within selected Langerhans cell populations can confuse this issue. Nevertheless, several investigators have shown that freshly isolated Langerhans cells are capable of producing macrophage inflammatory protein la (MlP-la), MIP-2, interleukin 12 (IL-12) and IL-15. In contrast, cultured Langerhans cells produce IL-1|3 and IL-6. When carefully controlled for keratinocyte

Figure 2 Human Langerhans cells within acetone-fixed epidermis stain with FITC-conjugated monoclonal antibody directed against CD1 a. To obtain epidermis, a blister was induced on the skin of the volar forearm using vacuum suction and heat and the blister roof (epidermal sheet) was removed using sterile scissors. Note the characteristic prominent dendritic processes.

Figure 2 Human Langerhans cells within acetone-fixed epidermis stain with FITC-conjugated monoclonal antibody directed against CD1 a. To obtain epidermis, a blister was induced on the skin of the volar forearm using vacuum suction and heat and the blister roof (epidermal sheet) was removed using sterile scissors. Note the characteristic prominent dendritic processes.

contamination, it is unclear whether Langerhans cells produce other known cytokines. Interestingly, cytokines produced by surrounding cells (i.e. keratinocytes) can greatly influence Langerhans cell phenotype and function. For example, granulocyte-macrophage colony-stimulating factor (GM-CSF) promotes growth of Langerhans cell precursors and potentiates immune function of Langerhans cells, tumor necrosis factor a (TNFa) promotes viability of Langerhans cells in culture and probably the emigration of Langerhans cells from epidermis, and IL-10 can decrease antigen presentation by Langerhans cells.

How To Bolster Your Immune System

How To Bolster Your Immune System

All Natural Immune Boosters Proven To Fight Infection, Disease And More. Discover A Natural, Safe Effective Way To Boost Your Immune System Using Ingredients From Your Kitchen Cupboard. The only common sense, no holds barred guide to hit the market today no gimmicks, no pills, just old fashioned common sense remedies to cure colds, influenza, viral infections and more.

Get My Free Audio Book


Post a comment