Phenotypic and functional analysis of Dendritic cells in Liver

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Dendritic cells (DCs) are a system of potent antigen-presenting cells that are distributed in lymphoid and nonlymphoid tissues where they are usually distinguished by their morphology and class II antigen expression. DCs in peripheral nonlymphoid tissues are thought to be a relatively immature cell type that capture antigens and migrate to T areas of the draining lymphoid organs. However, heterogeneity of DCs in nonlymphoid tissues is not well known. Therefore, the aim of this project is further characterization of DCs in terms of phenotype, function and distribution in the liver.A procedure was developed to maximize the yield of viable, nonparenchymal hepatic leukocytes by collagenase digestion of perfused liver fragments followed by density centrifugation with Nyco Prep^<TM>. FACS analyzes on isolates showed that N418 (CD11c)^+ cells are categorized into three different subpopulations besed on the cell size and the expression of class II,CD86 and DEC-205. All of them were CD3^-, CD4^-, and CD8^-, but strongly expressed CD45 and moderate levels of CD11b and CD44. The most immature DCs were small in size and negative or very little for class II,but expressed low level of B220. The intensity of class II was shown to correlate to the cell size. The large Class II^<high> cells with dendritic shape primarily localized in the triads but not in sinus, and CD11c^+ cells in sinus were negative for class II and relatively small round cells in immunohistochemical observation. When even small CD11c^+ cells, however, were cultured in the presence of GM-CSF for a few days, they became larger and increased class II,CD86 and DEC-205 expression, and potent allostimulatory activity was detected. These observations indicate that developmentally different populations of DCs are present in the distinguished part of the liver.