title: Lymphocyte subsets in neonatal and juvenile cats: comparison of blood and lymphoid tissues.
abstract: OBJECTIVE
  To compare lymphocyte subpopulations in the blood and lymphoid tissues of normal kittens between 1 and 90 days of age.
  
  
  METHODS
  Lymphocyte subsets within the blood, thymus, and lymph node of 24 normal kittens were quantified by use of two-color fluorescence flow cytometry and were compared at 1, 23, 46, or 90 days after birth.
  
  
  RESULTS
  Blood B and T lymphocytes increased over the 90-day postnatal period. The CD4+ and CD8+ sub-populations of T lymphocytes increased. However, CD8+ lymphocytes increased more than did CD4+ lymphocytes, resulting in reduced CD4-to-CD8 ratio. By 23 days of age, similar but more abrupt changes in the CD4-to-CD8 ratio occurred in the thymus and lymph nodes, coinciding with the highest thymus-to-body weight ratio and gradual increase in mature thymocytes expressing a pan-T lymphocyte marker.
  
  
  CONCLUSIONS
  Postnatal thymopoiesis in the domestic cat favors production of mature CD8+ T lymphocytes over CD4+ T lymphocytes. This coincides with the emergence of CD8+ lymphocytes in the lymph node and precedes a more gradual increase in CD8+ cells in the blood. Therefore, the ontogeny of these effectors of cell-mediated immunity could be interrupted by infective agents that target lymphoid tissues of the neonate.
authors.affiliation: Division of Comparative Medicine, College of Veterinary Medicine, University of Florida, Gainesville 32610-0880, USA.
authors.forename: S J
authors.initials: SJ
authors.lastname: Bortnick
authors.forename: M S
authors.initials: MS
authors.lastname: Orandle
authors.forename: G P
authors.initials: GP
authors.lastname: Papadi
authors.forename: C M
authors.initials: CM
authors.lastname: Johnson
mesh_terms: D000375:Aging; D000818:Animals; D000831:Animals, Newborn / Q000276:immunology*; D018791:CD4 Lymphocyte Count; D016516:CD4-CD8 Ratio; D002415:Cats / Q000254:growth & development* / Q000276:immunology*; D005260:Female; D008198:Lymph Nodes / Q000166:cytology; D018655:Lymphocyte Count; D016131:Lymphocyte Subsets; D008221:Lymphoid Tissue / Q000166:cytology*; D008297:Male; D012016:Reference Values; D013950:Thymus Gland / Q000166:cytology