Ikaros, present in naïve T cells, maintains a low level of histone acetylation. This, added to the high methylation status of histones restricts accessibility to the promoter such that key transcription factors (NF-AT, Oct-1) are unable to bind. T cell activation is associated with dramatic changes in histone methylation and acetylation, as well as in transcription factor binding. After cell activation has concluded, most transcription factors disengage from the IL2 promoter, but some (as Oct-1) remain attached. Likewise, although histone acetylation is lost, the locus is not re-methylated. This allows the cell a more rapid response upon re-activation.