DNA binding complexes are specific for IRE and SIE. Nuclear extracts from monocytes stimulated with IFN-γ (100 U/mL) and IL-10 (100 U/mL) were incubated with labeled IRE and competed with 100-fold molar excess of IRE, SIE, or SP-1 for DNA binding activity in gel mobility shifts (lanes 1 to 4). Reciprocally, nuclear extracts were incubated with labeled SIE and competed with 100-fold molar excess IRE, SIE, and SP-1 (lanes 5 to 8). Data are representative of 2 experiments.