Removal of Endotoxin and Cytokines by Adsorbents and the Effect of Plasma Protein Binding

High serum levels of endotoxin and cytokines, through which its activity is mediated, have been shown to be associated with disease severity in septic shock and in fulminant hepatic failure. In the present study, we have investigated the ability of activated charcoals (DHP-1 and Adsorba 150C) and uncharged resin (Amberlite XAD-7) to adsorb lipopolysaccharide (LPS) and various cytokines, namely tumour necrosis factor (TNF), interleukin-1 (IL-1), interleukin-6 (IL-6), interferon-α (IFN-α) and interferon-γ (IFN-γ). The capacities of the adsorbents were assessed by measurement of their equilibrium adsorption isotherms for these substances labelled with ¹²⁵I. There was no single adsorbent that uniformly adsorbed LPS and the cytokines from phosphate buffered saline or human plasma. DHP-1 charcoal was superior to Adsorba 150C for all substances and was the most effective adsorbent for binding LPS, IL-1α and IFN-γ. Amberlite XAD-7 resin was most effective for TNF, IL-6 and IFN-α, but bound little LPS, particularly from human plasma. Ultrafiltration through a membrane which retains substances of molecular weight > 50 kD did not filter the cytokines from human plasma, although the molecular weight of the cytokines range from 17 to 22 kD. This demonstrated that TNF, IL-1, IL-6, IFN-α and IFN-γ readily bind to proteins and/or other large molecules in plasma.