NFκB2/p100 Is a Key Factor for Endotoxin Tolerance in Human Monocytes: A Demonstration Using Primary Human Monocytes from Patients with Sepsis

Endotoxin tolerance (ET) is a state of reduced responsiveness to endotoxin stimulation after a primary bacterial insult. This phenomenon has been described in several pathologies, including sepsis, in which an endotoxin challenge results in reduced cytokine production. In this study, we show that the NF kappa L chain enhancer of activated B cells 2 (NF kappa B2)/p100 was overexpressed and accumulated in a well-established in vitro human monocyte model of ET. The p100 accumulation in these cells inversely correlated with the inflammatory response after LPS stimulation. Knocking down NF kappa B2/p100 using small interfering RNA in human monocytes further indicated that p100 expression is a crucial factor in the progression of ET. The monocytes derived from patients with sepsis had high levels of p100, and a downregulation of NF kappa B2/p100 in these septic monocytes reversed their ET status.