B‐ and T‐Lymphocyte Subset Numbers in the Migrating Lymphocyte Pool of the Rat: the Influence of Interferon‐γ on its Mobilization Monitored through Blood and Lymph

The subset composition of the migrating lymphocyte pool is largely unknown. In order to determine the number of B, T, CD8 +, CD4+ and CD4+‘naive’(CD45RC+) and ‘memory’ (CD45RC−) lymphocytes in this pool, the thoracic duct lymph of the rat was drained for 7 days. The effect of lymphocyte deplction on the number of blood lymphocytes was also monitored. In addition, the influence of continuously applied interferon-γ (IFN-α) on the mobilization of the migrating lymphocyte pool was investigated. Within 1 week 2 × 109 thoracic duct lymphocytes (TDL) were collected, which represents about 50% of the total lymphocyte pool of an adult rat. Among the migrating lymphocytes an early and a late mobilized population could be differentiated. In the former the CD4+‘naive’ (CD45RC+) T lymphocytes constituted the largest population, whereas in the latter it was the B lymphocytes. Continuous infusion of IFN-γ did not affect the number of lymphocytes in the blood. In contrast, in the thoracic duct IFN-γ reduced the appearance of all lymphocyte subsets. However, the pattern of reduction over time differed markedly depending on the population (early or late mobilized) and the phenotype (B- or T-tymphocyte subsets.