Fragile neutrophils in surgical patients: A phenomenon associated with critical illness

Abstract

Leukocyte viability (determined by e.g. propidium iodide [PI] staining) is automatically measured by hematology analyzers to check for delayed bench time. Incidental findings in fresh blood samples revealed the existence of leukocytes with decreased viability in critically ill surgical patients. Not much is known about these cells and their functional and/or clinical implications. Therefore, we investigated the incidence of decreased leukocyte viability, the implications for leukocyte functioning and its relation with clinical outcomes. An automated alarm was set in a routine hematology analyzer (Cell-Dyn Sapphire) for the presence of non-viable leukocytes characterized by increased fluorescence in the PI-channel (FL3:630 ±30nm). Patients with non-viable leukocytes were prospectively included and blood samples were drawn to investigate leukocyte viability in detail and to investigate leukocyte functioning (phagocytosis and responsiveness to a bacterial stimulus). Then, a retrospective analysis was conducted to investigate the incidence of fragile neutrophils in the circulation and clinical outcomes of surgical patients with fragile neutrophils hospitalized between 2013-2017. A high FL3 signal was either caused by 1) neutrophil autofluorescence which was considered false positive, or by 2) actual non-viable PI-positive neutrophils in the blood sample. These two causes could be distinguished using automatically generated data from the hematology analyzer. The non-viable (PI-positive) neutrophils proved to be viable (PInegative) in non-lysed blood samples, and were therefore referred to as 'fragile neutrophils'. Overall leukocyte functioning was not impaired in patients with fragile neutrophils. Of the 11 872 retrospectively included surgical patients, 75 (0.63%) were identified to have fragile neutrophils during hospitalization. Of all patients with fragile neutrophils, 75.7% developed an infection, 70.3% were admitted to the ICU and 31.3% died during hospitalization. In conclusion, fragile neutrophils occur in the circulation of critically ill surgical patients. These cells can be automatically detected during routine blood analyses and are an indicator of critical illness.

Flow cytometric evaluation of the neutrophil compartment in COVID-19 at hospital presentation: A normal response to an abnormal situation

“…7 The pathophysiology of ARDS is normally mediated by malfunctioning of the neutrophil compartment leading to accumulation and specific activation of these cells in the pulmonary tissue, which in turn causes collateral damage characterized by destruction of epithelial and endothelial cells. [8][9][10][11][12] Tissue damage is caused by neutrophil-driven mechanisms that are normally employed to kill microorganisms, which include production of reactive oxygen species, degranulation of toxic proteins and enzymes, and netosis. 10,13,14 This leads to increased vascular permeability and protein-rich alveolar edema causing decreased gas exchange and hypoxemia.…”

“…The ARDS found in COVID‐19 patients is characterized by decreased oxygenation and rapid respiratory failure 7 . The pathophysiology of ARDS is normally mediated by malfunctioning of the neutrophil compartment leading to accumulation and specific activation of these cells in the pulmonary tissue, which in turn causes collateral damage characterized by destruction of epithelial and endothelial cells 8–12 . Tissue damage is caused by neutrophil‐driven mechanisms that are normally employed to kill microorganisms, which include production of reactive oxygen species, degranulation of toxic proteins and enzymes, and netosis 10,13,14 .…”

Analysis of human neutrophil phenotypes as biomarker to monitor exercise-induced immune changes

“…The innate immune system demonstrates the most pronounced changes after prolonged exercise 17 . The primary effector cells of the innate immune system are granulocytes and monocytes 21–23 . Receptor expression on these cells, measured by flow cytometry, has proven to give insight into the status of the innate immune system 24–26 …”

“…17 The primary effector cells of the innate immune system are granulocytes and monocytes. [21][22][23] Receptor expression on these cells, measured by flow cytometry, has proven to give insight into the status of the innate immune system. [24][25][26] A recent study showed that intensive exercise led to the mobilization of neutrophil phenotypes associated with systemic inflammation and immunosuppression.…”

Insights into the trafficking of human leukocytes to colostrum evidences a modulation of the B lymphocyte compartment in obesity

“…However, small and large subpopulations of monocytes have recently been described in peripheral blood in healthy state, with classical CD16monocytes comprising the majority of populations of both sizes, and cell-size dependent responses to stimulation within donors, which supports size differences being an actual phenotype unlinked to cell death 38 . In addition, the neutrophil fraction, which is the most delicate leukocyte cell subtype with high sensitivity to shear stress and temperature changes, did not present a significant variation in size between tissues, casting doubt on apoptosis being the cause for all observed cell shrinkage 39,40 . Differential isotonic pressure of tissue significantly impacts the size of leukocytes, which may be an alternative explanation for size differences observed as breastmilk has higher osmolality than peripheral blood 41,42 .…”