Dendritic Cells (DCs)

Residing at the interface of innate and adaptive immunity, DCs are a heterogeneous family of circulating and tissue resident immune cells that based on their cellular origins are assigned to one of two distinct subsets. Myeloid-derived DCs (mDCs), which include Langerhans cells (LCs) in the skin and conventional DCs (cDCs) in the blood assist, in the case of LCs, in the initiation of adaptive immune responses whereas DCs of lymphoid descent, which are represented by blood-borne plasmacytoid DCs (pDCs) are involved in anti-viral immune responses via their secretion of IFN-a.

Human-based immunogerontological studies that have investigated the impact of age on DC number have focused primarily upon those subsets present in peripheral blood, namely cDCs and pDCs. Whilst age appears to have no effect upon the frequency of cDCs [71-73] , its impact on pDCs is unclear, with some studies revealing a marked reduction in the percentage and/or absolute number of this DC subset with age [72-74], and others reporting no difference between young and older adults [71, 75]. In respect of tissue-resident DCs, a significant age-associated reduction in the frequency of LCs has been described [76].

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