Overview of computational model.

The model incorporates the formation of receptor-ligand complex from extracellular IL-2 and receptor subunits at the cell membrane (1–4). The complex is internalized (5) and its components sorted for intracellular degradation (8) or recycling (9). The binding of IL-2 by its receptor initiates a downstream signaling cascade that results in translocation of STAT5 from the cytosol to the nucleus (13). This is represented by a delay function affected by the number of receptor-ligand complexes present at the cell membrane. The model also incorporates constitutive (11) and IL-2 induced (12) production of receptor subunits and consecutive internalization of unbound receptor (10). Dashed arrows indicate an effect of a species on a reaction. Numbers by reaction arrows correspond to process numbers in Table 1.