Abstract
HNL (human Neutrophil Lipocalin) is a protein secreted from the activated neutrophil granulocytes but also from epithelial cells. HNL is measured by sensitive immunoassays in most bodily fluids and exists in several variants of which the monomer and the dimer variants are the most abundant. Depending on the antibody configuration of the immunoassays we may detect different molecular variants of HNL, and which may have different cellular origins. The dimeric form of HNL is entirely neutrophil specific and other assays may preferentially detect HNL originating from epithelial cells such as the tubular cells of the kidney. In this brief review we have focused on the utility of HNL as a biomarker for antibiotics stewardship in patients with sepsis and show that the dimeric form of HNL is reduced within 24 hours as the response to successful antibiotic treatment in sepsis in contrast to the reduction of blood levels of procalcitonin and heparin-binding protein which takes 3-4 days. Another variant of HNL showed to be the most powerful predictor of outcome of these patients. We conclude that the measurements of these HNL variants should be considered for implementation in intensive care units and other settings with seriously ill infected patients.