CHANGES IN LYMPHOCYTE SUBSETS WITH AGE IN PERINATAL CATS - LATE-GESTATION THROUGH 8 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 funct ion of increases in total lymphocyte numbers while proportions of thes e subsets remained relatively static. In contrast, both the total numb er and proportion of Ig(+) cells increased from birth to 4 weeks of ag e, after which there were essentially no changes. Null (pan-T-, Ig(-)) cells were highest during late gestation and declined steadily therea fter to become a minimal component of the peripheral lymphocyte subset s. Compared with normal adult values, CD4/CD8 ratios were high through out the 8 week study period, These results illustrate that the neonata l cat blood lymphocyte profile undergoes maturational changes and emph asize the importance of evaluating age-matched controls in studies of conditions that may alter feline lymphocyte subsets.