Age related changes in lymphocyte sub-populations in peripheral blood of healthy weaned piglets

Abstract

The aim of the presented study was to characterise the development of the cellular part of the immune system in pigs from 1 d to 20 weeks of age. Haematological examination and flow cytometry were used to establish the relative and absolute counts of various leukocyte subsets. During the first 5 months of pig life, a significant age-dependent increase in lymphocyte and granulocyte counts was noted. Moreover, a decrease in relative size of lymphocytes connected with increasing proportion of granulocytes was observed. The absolute size of CD3+ and CD21+ increased approximately two-fold during the analysed period. The absolute number of CD4+CD8- , CD4-CD8+ and CD4+CD8+ cells increased almost twice from birth till the 6th week of age. After this time, only CD4+CD8- subset remained stable, while the number of CD4-CD8+ and CD4+CD8+ subsets gradually increased 1.5- and 2.5-fold from 6 weeks to 5 months of age for CD4-CD8+ and CD4+CD8+ , respectively. In conclusion, changes in the absolute size of lymphocyte subsets are not always consistent with changes in their relative size. Moreover, because there are age-related differences in leukocyte subsets in porcine blood, there is a need to use appropriate age matched control groups, especially in experiments, which include immunophenotyping of lymphocytes. We suggest that immunophenotyping of lymphocytes, especially for diagnostic purposes, should be based on the absolute size rather than on the percentage of lymphocyte subpopulations.