Sustained silencing of potentially autotoxic acute proinflammatory genes like TNFa occurs in circulating leukocytes following the early phase of severe systemic inflammation. Aspects of this gene reprogramming suggest the involvement of epigenetic processes. We used THP-1 human promonocytes, which mimic gene silencing when rendered endotoxin tolerant in vitro, to test whether TNFa proximal promoter nucleosomes and transcription factors adapt to an activation-specific profile by developing a characteristic chromatin-based silencing marks. We find increased TNFa mRNA levels in endotoxin responsive cells that is preceded by dissociation of heterochromatin binding protein 1a (HP1a), demethylation of nucleosomal histone H3 lysine 9 (H3 Lys9), increased phosphorylation of the adjacent serine 10 (H3 Ser10), and recruitment of NF-B RelA/p65 to the TNFa promoter. In contrast, endotoxin tolerant cells repress production of TNFa mRNA, retain binding of HP1a, sustain methylation of H3(Lys9), reduce phosphorylation of H3(Ser10), and diminish binding of NF-B RelA/p65 to the TNFa promoter. Similar levels of NF-B p50 occur at the TNFa promoter in the basal state, during active transcription, and in the silenced phenotype. Induction of RelB, which acts as a repressor of TNFa transcription, remains bound to the promoter during silencing. These results support an immunodeficiency paradigm where epigenetic changes at the promoter of acute proinflammatory genes mediate their repression during the late phase of severe systemic inflammation.