Aging Aging

Dendritic Cells in Old Age 29122Dendritic Cells in Old AgeBeatrix Grubeck-Loebenstein, Maria Saurwein-Teissl,and Nikolaus Romani1. Introduction1.1. General BackgroundDendritic cells (DCs) are powerful antigen-presenting cells that have the uniquecapacity to stimulate naive T-cells (1,2). DCs are identified by a triad of criteria:Morphologically, they exhibit pronounced cytoplasmic veils that are mobile andcan easily be observed under a phase-contrast microscope. These veils becomeapparent only in the mature state. Phenotypically, they express high levels ofmajor histocompatibility class (MHC) (class I and II), adhesion (CD11c, CD54,CD58), and costimulatory (CD80, CD86, CD40) molecules on their cell surfaces.They also express CD1a and CD83, but lack CD14. On cytocentrifugesmears stained with anti-CD68, a marker of the endocytic system that is abundantin macrophages, DCs display spotlike staining whereas typical macrophagesare strongly positive all over the cytoplasm. When looking at forward/side scatterprofiles in the fluorescence-activated cell sorter (FACS), DCs show highlight scattering and are outside the typical lymphocyte gate. Functionally, theyare potent stimulators of resting T lymphocytes in the allogeneic mixed leukocytereaction. DCs derived from various tissues have been shown to undergo acomplex maturation process during which their morphology, phenotype, andfunction change. DCs are derived from bone marrow progenitors and circulatein the blood as immature precursors before they migrate into peripheral tissues,such as the epidermis, heart, lung, liver, gut, thymus, spleen, and lymph nodes.DCs of myeloid as well as of lymphoid origin have been described (3–5). Withintissues DCs take up and process antigen which is then presented in the contextof MHC molecules. Upon appropriate stimulation they undergo further maturationand migrate to secondary lymphoid tissue where they present antigens toFrom: Methods in Molecular Medicine, Vol. 38: Aging Methods and ProtocolsEdited by: Y. A. Barnett and C. R. Barnett © Humana Press Inc., Totowa, NJ291