Removal of activated neutrophils by a polymyxin B-immobilized fiber (PMX) column

Background: Polymyxin B-immobilized fiber (PMX) columns are used to treat endotoxemic septic shock and have also been considered for the acute exacerbation of idiopathic pulmonary fibrosis (AE-IPF), a condition defined by the absence of infection. Since the potential therapeutic effects beyond endotoxin adsorption remain unclear, we investigated the in vitro adsorption of various leukocyte subtypes using PMX columns under controlled stimulation. Methods: Whole blood from six healthy donors was treated with or without llipopolysaccharide (LPS) to model leukocyte activation. Leukocyte subsets and activation (CD11b + ) were quantified by flow cytometric analysis before and after hemoperfusion through PMX or control columns. Removal capacity (%) and changes in neutrophil-to-lymphocyte ratio (NLR) were calculated. Results: The removal capacities of monocytes, granulocytes, and neutrophils were significantly higher with PMX column hemoperfusion than with the control column, with more pronounced effects after LPS stimulation. Lymphocyte removal was not significant. Activated CD11b + granulocytes and neutrophils were preferentially removed by PMX columns. NLR was significantly reduced only by PMX columns, and the rate of change in NLR correlated with neutrophil removal, with a higher coefficient of determination in LPS-treated blood. Conclusions: PMX columns preferentially removed activated granulocytes/neutrophils and reduced NLR in vitro. These findings provide hypothesis-generating mechanistic insights into how PMX may modulate activated leukocyte profiles beyond endotoxin adsorption.