title: Alterations to the frequency and function of peripheral blood monocytes and associations with chronic disease in the advanced-age, frail elderly.
abstract: BACKGROUND
  Circulating myeloid cells are important mediators of the inflammatory response, acting as a major source of resident tissue antigen presenting cells and serum cytokines. They represent a number of distinct subpopulations whose functional capacity and relative concentrations are known to change with age. Little is known of these changes in the very old and physically frail, a rapidly increasing proportion of the North American population.
  
  
  METHODS
  In the following study the frequency and receptor expression of blood monocytes and dendritic cells (DCs) were characterized in a sample of advanced-age, frail elderly (81-100 yrs), and compared against that of adults (19-59 yrs), and community-dwelling seniors (61-76 yrs). Cytokine responses following TLR stimulation were also investigated, as well as associations between immunophenotyping parameters and chronic diseases.
  
  
  RESULTS
  The advanced-age, frail elderly had significantly fewer CD14(++) and CD14(+)CD16(+), but not CD14(++)CD16(+) monocytes, fewer plasmacytoid and myeloid DCs, and a lower frequency of monocytes expressing the chemokine receptors CCR2 and CX3CR1. At baseline and following stimulation with TLR-2 and -4 agonists, monocytes from the advanced-age, frail elderly produced more TNF than adults, although the overall induction was significantly lower. Finally, monocyte subset frequency and CX3CR1 expression was positively associated with dementia, while negatively associated with anemia and diabetes in the advanced-age, frail elderly.
  
  
  CONCLUSIONS
  These data demonstrate that blood monocyte frequency and phenotype are altered in the advanced-age, frail elderly and that these changes correlate with certain chronic diseases. Whether these changes contribute to or are caused by these conditions warrants further investigation.
authors.affiliation: Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario, Canada.
authors.forename: Chris P
authors.initials: CP
authors.lastname: Verschoor
authors.affiliation: Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, Ontario, Canada.
authors.forename: Jennie
authors.initials: J
authors.lastname: Johnstone
authors.affiliation: Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario, Canada.
authors.forename: Jamie
authors.initials: J
authors.lastname: Millar
authors.affiliation: Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario, Canada.
authors.forename: Robin
authors.initials: R
authors.lastname: Parsons
authors.affiliation: Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario, Canada.
authors.forename: Alina
authors.initials: A
authors.lastname: Lelic
authors.affiliation: Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario, Canada; Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, Ontario, Canada; Department of Medicine, McMaster University, Hamilton, Ontario, Canada; Institute for Infectious Diseases Research, McMaster University, Hamilton, Ontario, Canada.
authors.forename: Mark
authors.initials: M
authors.lastname: Loeb
authors.affiliation: Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario, Canada; Institute for Infectious Diseases Research, McMaster University, Hamilton, Ontario, Canada.
authors.forename: Jonathan L
authors.initials: JL
authors.lastname: Bramson
authors.affiliation: Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario, Canada; Institute for Infectious Diseases Research, McMaster University, Hamilton, Ontario, Canada.
authors.forename: Dawn M E
authors.initials: DM
authors.lastname: Bowdish
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging; D002908:Chronic Disease; D016207:Cytokines / Q000032:analysis / Q000276:immunology*; D003713:Dendritic Cells / Q000166:cytology / Q000276:immunology; D005260:Female; D016330:Frail Elderly; D006801:Humans; D016130:Immunophenotyping; D018950:Lipopolysaccharide Receptors / Q000032:analysis / Q000276:immunology; D008297:Male; D008875:Middle Aged; D009000:Monocytes / Q000166:cytology / Q000276:immunology*; D051195:Toll-Like Receptor 2 / Q000276:immunology; D051197:Toll-Like Receptor 4 / Q000276:immunology; D055815:Young Adult
chemical_list: D016207:Cytokines; D018950:Lipopolysaccharide Receptors; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4
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