Mitotic activity of thoracic duct cells in rabbits correlates with age and total lymphocyte numbers

Abstract

Th e aim of this study was to assess correlations between rabbit mitotic thoracic duct (TD) cells, rabbit's age, and TD lymphocytes. Th e experiments were carried out in 27 intact male Chinchilla rabbits weighing 120-2.500 g (at the age of 1.5 weeks to 36 weeks). TD lymph specimens were drawn from the cisterna chyli of anaesthetised rabbits. Th e numbers of mitotic cells from TD per 100 cells, and absolute numbers of TD lymphocytes were counted in the Giemsa-stained cell smears by means of routine light microscope methods, and routine hemocytometric counts. We have performed statistical evaluation of the data by Microsoft Offi ce Excel 2007 soft ware. Correlations between the TD mitotic cell ratio, lymphocyte numbers, and animal age was estimated by Pearson's criteria. Th e mitotic cell number in TD lymph decreased from the age of 1.5 weeks (infant animals) to 36 weeks (young adult rabbits). Maximal mitotic activity was found in rabbits at 1.5 week of age (23.0 ± 0.14, P=0.02) in comparison with appropriate indexes in rabbits at 4.5 and 13.5 weeks of age (11.0 ± 0.14*, P<0.05 and 6.3 ± 0.08**, P<0.001 respectively). In contrast to mitotic cell amounts, the absolute TD lymphocyte numbers were increased in older rabbits. Th e minimal TD; lymphocyte number in the 1.5-week old rabbits aged was 2.8 ± 0.03, being signifi cantly diff erent (P=0.04) against the lymphocyte numbers in rabbits aged 36 week (5.9 ± 0.05, P=0.03). Hence, strong negative correlations were found between the TD mitotic activity and age, mitotic cells and total TD lymphocyte numbers, as well as positive correlation between the TD lymphocytes and age (respectively, R 2 =0.7, R 2 =0.96 and R 2 =0.8) in immature rabbits (age from 1.5 weeks to 36 weeks). To our knowledge, these interrelations for TD lymph cells in the very young animals were detected for the fi rst time. We conclude that the age-related correlation between mitotic activity and total lymphocyte amounts in TD allows presume optimal combinations of cytokines and other bioactive factors that regulate mitotic activity of thoracic duct cells with advancing age.