The Short-Lived Lymphocyte in the Thymus Cortex of the Rat

Abstract

It was attempted to assess the life span of tritiated deoxycyti-dine ([3H]CdR) labeled lymphocytes after intravenous transfusion into young rats and compare their homing pattern with previous results obtained with tritiated thymidine ([3H]TdR) labeled lymphocytes. Only cortical thymocytes were labeled by administering [3H]CdR according to Weissman's transcapsular route. Such labeled cortical thymocytes were transfused intravenously into young recipient rats. The results obtained from these experiments showed that almost all labeled cells disappeared within 24 h after transfusion and practically no labeled cells were detected in the thoracic duct lymph (TDL). Minutes after the transfusion, many labeled lymphocytes were found in the lung, liver, bone marrow and kidney but 24 h later only the spleen contained a certain number of labeled cells, mainly in T-dependent areas and the red pulp. At later times, practically all labeled cells had disappeared. These observations indicate that [3H]CdR labeled cortical thymocytes are short lived and practically none of them recirculate from blood through TDL.