A – Signaling pathways downstream if TCR and CD28 as exemplified by modulation of IL-2 expression in T helper cells according to Gaffen SL and Liu KD . In gray are genes whose expression was not significantly affected by rIL-2, in green those significantly down-regulated and in red those significantly up-regulated. B – Clusterogram of genes shown in panel A. Light blue and red horizontal bares underline PBMC sample from Caucasian and Chinese donors; in separate panels CD4 (small red horizontal bar) and CD8 T cells (light blue bar) exposed to rIL-2 in the presence of PBMC and subsequently isolated are compared with CD4 and CD8 T cells (orange and dark blue horizontal bars respectively) purified before exposure to rIL-2. The dashed orange arrow points at the expression of CISH in the clusterogram. Ratios are displayed according to the central method for display using a normalization factor .