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Lymphocyte subsets in neonatal and juvenile cats: comparison of blood and lymphoid tissues
S J Bortnick1, M S Orandle, G P Papadi
1Division of Comparative Medicine, College of Veterinary Medicine, University of Florida, Gainesville 32610-0880, USA.
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.
