Dendritic cells from human blood : Antigen handling and expression of adhesion molecules

• Dendritic cells are a system of professional antigen-presenting cells that initiate the immune responses. Dendritic cells are widely distributed in the body, both in nonlymphoid tissues, lymphoid tissues and fluids of the body. Dendritic cells arise from the bone marrow and can be classified into interstitial dendritic cells in nonlymphoid tissues, interdigitating dendritic cells in secondary lymphoid tissue, dendritic cells in blnod and veiled cells in lymphatics. They can exhibit differences in each of these compartments that relate to maturation state and microenvironment.Dendritic cells process and present antigens efficiently in situ and stimulate responses from naive and memory T cells in the paracortical area of secondary lymphoid organs. Properties contributing to the dendritic cells' specialized function are the efficiency in clustering T cells and giving the right signals needed to activate naive and resting T cells. The present work was focused on elucidating some key properties of DC biology. The results show that mature human blood dendritic cells express sialyl Lewis x (CD15s), sialyl Lewis a, CD44 and CD77. Adhesion of mature blnod dendritic cells to activated endothelium (human umbilical cord endothelial cells) involves Eselectin. Immature blnod (cytokine-driven) dendritic cells use FcyRII for uptake of IgG immune complexes. Annexin V is involved in antigen trafficking in the endocytotic pathway of soluble proteins in mature blood dendritic cells. Immature blood dendritic cells (cytokine-driven) have the capacity to handle uptake of both soluble and microbial antigens, via fluid-phase pinocytosis, receptor-mediatedendocytosis and phagocytosis. No productive infection of influenza virus and no exogenous ll..-2 is demanded when dendritic cells are used as antigen-presenting cells. Dendritic cells induce cytotoxic T cells even with attenuated influenza A virus.

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