FOS and tuberculosis: Although inducible DHSs (iDHSs) are opened up transiently by factors such as AP-1 and NFAT, and typically function as inducible transcriptional enhancers or promoters, ∼3,000 of the DHSs formed during blast cell transformation are stably maintained as primed DHSs (pDHSs) in TB and in memory T cells without influencing steady-state transcription.