The Cellular Response Capacity as Diagnostic Head Start in Neutrophil Endotoxemia Sensing

Early detection of endotoxemia-related systemic inflammation remains a major unmet diagnostic need. Established inflammatory biomarkers largely reflect downstream protein biosynthesis and therefore rise with delay. Direct monitoring of rapid leukocyte phenotype changes, particularly in neutrophils, may provide an earlier readout, but insufficient standardization has limited clinical translation. Using flow cytometry, we established the neutrophil cellular response capacity (CRC) in a controlled ex vivo human whole-blood model of endotoxemia employing intact lipopolysaccharide (LPS) as a defined prototypical pathogen-associated molecular pattern. The performance of the neutrophil CRC was thoroughly characterized and compared to conventional humoral inflammatory markers with respect to their ability to detect endotoxemia. Screening identified CD10, CD11b, and CD66b as the best-performing CRC markers, detecting prior LPS exposure at concentrations in the low pg/mL range. In the dynamic continuum of inflammation, encompassing cellular phenotype shifts, functional changes, and subsequent humoral response, the CRC of neutrophils reliably detected very early phenotypic alterations, surpassing the sensitivity of classical clinical inflammation markers in our human blood endotoxemia model. In summary, the CRC represents a proof-of-concept approach for standardized early cellular immunomonitoring in ex vivo endotoxemia. Further evaluation in more heterogeneous inflammatory settings and in patients with systemic inflammation or sepsis is warranted.