title: Age-related quantitative alterations in lymphocyte subsets and immunoglobulin isotypes in healthy horses.
abstract: OBJECTIVE
  To characterize age-associated changes in lymphocyte population subsets and immunoglobulin isotypes.
  
  
  METHODS
  30 healthy young light-breed horses (5 to 12 years old) and 30 healthy aged light-breed horses (> 20 years old).
  
  
  METHODS
  Lymphocyte subset populations were identified, using monoclonal antibodies to cell surface markers CD5, CD4, CD8, and IgG. Subset populations were quantitated by use of flow cytometric analysis of antibody-stained cells. Serum immunoglobulin concentration was determined using single radial immunodiffusion.
  
  
  RESULTS
  Absolute cell counts of total lymphocytes, T cells, CD4+ and CD8+ T cells, and B cells were decreased in aged horses, compared with young horses. There was a significant decrease in the percentage of CD8+ cells and an increase in the CD4+-to-CD8+ cell ratio in the aged population, compared with young horses. However, serum concentration of IgG, IgG(T), IgM, or IgA did not differ with age.
  
  
  CONCLUSIONS
  In horses, total lymphocyte count and lymphocyte subset cell counts decrease with age. Age-matched control values are necessary for optimal evaluation of hematologic variables in aged horses. The decrease in lymphocyte subset cell counts in healthy aged horses mimics that seen in other species and may contribute to an age-associated decrease in immunocompetency.
authors.affiliation: Department of Food Animal and Equine Medicine, College of Veterinary Medicine, North Carolina State University, Raleigh 27606, USA.
authors.forename: D
authors.initials: D
authors.lastname: McFarlane
authors.forename: D C
authors.initials: DC
authors.lastname: Sellon
authors.forename: S A
authors.initials: SA
authors.lastname: Gibbs
mesh_terms: D000367:Age Factors; D000818:Animals; D005260:Female; D005434:Flow Cytometry / Q000662:veterinary; D006736:Horses / Q000276:immunology*; D005779:Immunodiffusion / Q000662:veterinary; D007132:Immunoglobulin Isotypes / Q000276:immunology*; D016131:Lymphocyte Subsets / Q000276:immunology*; D008297:Male; D012044:Regression Analysis; D018709:Statistics, Nonparametric
chemical_list: D007132:Immunoglobulin Isotypes