title: Intraindividual variability and the effect of acute illness on immune senescence markers.
abstract: OBJECTIVE
  To determine the intraindividual variability and effect of acute illness on two markers of immune senescence.
  
  
  METHODS
  Cohort study with repeated measures.
  
  
  METHODS
  Clinical research center and emergency department at two academic medical centers.
  
  
  METHODS
  Seventy-three subjects aged 65 and older enrolled in three groups: chronic underlying conditions but no acute illness, acutely ill with infection (community-acquired pneumonia), and acutely ill without infection.
  
  
  METHODS
  CD16 density on polymorphonuclear neutrophils (PMNs) and the proportion of CD8+ T cells that express CD28 determined twice in the nonacutely ill group and three times (Days 0, 30, and 60) in the acute illness groups.
  
  
  RESULTS
  In the nonacutely ill group, PMN CD16 density demonstrated wide intraindividual variation, but there was a strong correlation for repeated measures of the percentage of CD8+ T cells expressing CD28 (correlation coefficient (r)=0.77, P<.001). Acute illness markedly affected both measures, regardless of whether the illness was due to infection; there was no correlation between measures obtained on Day 0 versus Day 30 for either immune marker. In contrast, a strong correlation existed between Day 30 and Day 60 values, particularly for CD8+/CD28+ percentage (r=0.58-0.86; P=.006 to <.001).
  
  
  CONCLUSIONS
  The percentage of CD8+ T cells that express CD28 is a highly reproducible marker of immune senescence. Although acute illness affects this marker, 30 to 60 days of convalescence appears adequate for it to return to baseline.
authors.affiliation: Department of Internal Medicine, Section of Infectious Diseases, Wake Forest University Health Sciences, Winston-Salem, North Carolina 27157, USA. khigh@wfubmc.edu
authors.forename: Kevin P
authors.initials: KP
authors.lastname: High
authors.forename: Melissa
authors.initials: M
authors.lastname: Trader
authors.forename: Marco
authors.initials: M
authors.lastname: Pahor
authors.forename: Mark
authors.initials: M
authors.lastname: Loeb
mesh_terms: D000208:Acute Disease; D000367:Age Factors; D000368:Aged; D018106:CD28 Antigens / Q000097:blood; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D002908:Chronic Disease; D017714:Community-Acquired Infections / Q000276:immunology*; D005260:Female; D015577:Geriatric Assessment; D006801:Humans; D007155:Immunologic Factors / Q000097:blood*; D007206:Individuality; D018655:Lymphocyte Count; D008297:Male; D009504:Neutrophils / Q000276:immunology; D018410:Pneumonia, Bacterial / Q000276:immunology*; D017452:Receptors, IgG / Q000097:blood; D015203:Reproducibility of Results; D013223:Statistics as Topic
chemical_list: D018106:CD28 Antigens; D007155:Immunologic Factors; D017452:Receptors, IgG