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Journal of Clinical Immunology

, Volume 30, Issue 6, pp 806–813

First Online: 12 August 2010Received: 30 June 2010Accepted: 22 July 2010


Aging is associated with increased susceptibility to microbial infections, and monocytes play an important role in microbial defense. In this study, we have identified and compared four subpopulations of monocytes CD14CD16, CD14CD16, CD14CD16, and CD14CD16 in the peripheral blood of young and aged subjects with regard to their numbers, cytokine production, TLR expression, and phosphorylation of ERK1-2 in response to pam3Cys a TLR-1-2 ligand. Proportions and numbers of CD14CD16 and CD14CD16 monocytes were significantly increased, whereas proportions of CD14CD16 monocytes were decreased in aged subjects as compared to young subjects. In aged subjects, IL-6 production by all four subsets of monocytes was significantly decreased, whereas TNF-α production was decreased in monocyte subsets, except the CD14CD16 subset. A significantly reduced expression of TLR1 was observed in CD14CD16 and CD14CD16 monocyte subsets in aged subjects. Furthermore, following pam3Cys stimulation, ERK1-2 phosphorylation was significantly lower in CD14CD16, CD14CD16, and CD14CD16 subsets of monocytes from aged subjects. This is the first study of four subpopulations of monocytes in aging, which demonstrates that their functions are differentially impaired with regard to the production of cytokines, expression of TLR, and signaling via the ERK–MAPK pathway. Finally, changes in the number of monocyte subsets, and impairment of TLR1 expression, TNF-α production, and EK1-2 phosphorylation was more consistent in CD16 monocyte subsets regardless of expression of CD14 or CD14, therefore highlighting the significance of further subdivision of monocytes into four subpopulations.

KeywordsTLR monocyte subsets cytokines signaling  Download fulltext PDF

Autor: Joseph Nyugen - Sudhanshu Agrawal - Sastry Gollapudi - Sudhir Gupta


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