Changes in lymphocyte subsets with age in perinatal cats: late gestation through eight weeks

The age-related changes in numbers and proportions of peripheral blood lymphocyte subsets (pan-T, CD4, CD8, Ig, and null) were evaluated by two-color flow cytometry in 16 feline fetuses (56–58 days gestational age) and 21 kittens from birth through 8 weeks of age. Populations of pan-T+, CD4+, and CD8+ cells increased in total numbers as a function of increases in total lymphocyte numbers while proportions of these subsets remained relatively static. In contrast, both the total number and proportion of Ig+ cells increased from birth to 4 weeks of age, after which there were essentially no changes. Null (pan-T−), Ig− cells were highest during late gestation and declined steadily thereafter to become a minimal component of the peripheral lymphocyte subsets. Compared with normal adult values, CD4CD8 ratios were high throughout the 8 week study period. These results illustrate that the neonatal cat blood lymphocyte profile undergoes maturational changes and emphasize the importance of evaluating age-matched controls in studies of conditions that may alter feline lymphocyte subsets.