Peripheral blood T lymphocytes require two signals to enter and progress along the cell
cycle from their natural quiescent state. The first activation signal is provided by the
stimulation through the T cell receptor, which induces the synthesis of cyclins and the
expression of the high affinity interleukin-2 receptor. The second signal, required to enter the
S phase, is generated upon binding of interleukin-2 to the high affinity αβγ interleukin-2
receptor. However, resting T cells already express intermediate affinity βγ interleukin-2 …