Plasmacytoid dendritic cells and their Toll-like receptor 9 expression selectively decrease with age

Dendritic cells (DCs) play a crucial role in the initiation of immune responses against infectious particles and tumor cells; however, the impact of age, anthropometric parameters, and gender on the number and the expression of function-associated molecules of human DCs is poorly understood. In this study, blood DCs of 50 volunteers (19 - 84 years old) with no acute or chronic inflammatory diseases were examined using 4-color flow cytometry. Increasing age was associated with a decrease in blood plasmacytoid, but not myeloid DCs and a selective decrease in Toll-like receptor 9 (TLR9) expression by plasmacytoid DCs. In contrast, gender and body mass index did not impact the number of DC subsets or the expression of function-associated DC molecules. Thus, we demonstrate that age has a selective impact on plasmacytoid DCs and their TLR9 expression. This may contribute to an increased susceptibility to infections and tumors with increasing age. (C) 2012 American Society for Histocompatibility and Immunogenetics. Published by Elsevier Inc. All rights reserved.