Subpopulations of Mouse T Lymphocytes

The existence of short-lived peripheral T lymphocytes was directly investigated using an in vitro system. Spleen and lymph node cell suspensions from normal LAF1 mice were pulse-treated for 1 hr in vitro with high specific activity tritiated thymidine (“thymidine suicide”). Thymidine suicide allows for the selective, lethal irradiation of those cells which are actively synthesizing DNA, i.e., proliferating cells in S phase, during the pulse period. To determine the “suicide” (loss or inactivation) of T lymphocytes, the isotope-treated cells were stimulated with phytohemagglutinin (PHA). The results showed that: a) a population of dividing (proliferating) T lymphocytes exists in the spleen; b) these cells are not present in lymph nodes; and c) with respect to the spleen, it is the dividing T lymphocytes which are primarily responsible for the PHA response.