Our studies addressed the mechanism by which serum acts in conjunction with T cell
receptor (TCR) agonists to promote the proliferation of primary splenic T cells. When added
to resting splenocytes, TCR agonists initiated G 0/G 1 traverse and activated cyclin D3-cdk6
complexes in a serum-independent manner. On the other hand, both TCR agonists and 10%
serum were required for the activation of cyclin E-cdk2 and cyclin A-cdk2 complexes and the
entry of cells into S phase. Serum facilitated cdk2 activation by maximizing the extent and …