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Intercellular cell adhesion molecule 1 (ICAM-1) is a cell surface glycoprotein with a vital role in the immune response to pathogens. The expression pattern of ICAM-1 is wide ranging, encompassing endothelial cells, epithelial cells, and neutrophils. Recent work has characterized the role of ICAM-1 in murine neutrophils, but the function of human neutrophil ICAM-1 is incompletely understood. Herein, we investigated the expression and role of ICAMs in human neutrophils in vitro and in vivo. Our findings show clear expression of ICAM-1, -3, and -4 on peripheral blood–derived neutrophils and demonstrate that the pathogen-associated molecular pattern lipoteichoic acid is an inducer of ICAM-1 expression in vitro. In vivo, neutrophils obtained from the pleural cavity of patients with a parapneumonic effusion display enhanced expression of ICAM-1 compared with peripheral blood– and oral cavity–derived neutrophils. Moreover, migration of peripheral blood–derived neutrophils across endothelial cells can upregulate neutrophil ICAM-1 expression. These findings indicate that pathogen-associated molecular patterns and/or cytokines, alongside transmigration, enhance neutrophil ICAM-1 expression at sites of inflammation. Mechanistically, we observed that ICAM-1high neutrophils display elevated S. aureus phagocytic capacity. However, unlike murine neutrophils, ICAM-1 intracellular signaling in human neutrophils was not essential for phagocytosis of Staphylococcus aureus and reactive oxygen species generation. Taken together, these results have important implications for the regulation of neutrophil-mediated pathogen clearance. [ABSTRACT FROM AUTHOR]

The document proposes a minimally-invasive assay to identify individuals with specific inborn errors of innate immunity (IEIs) by testing for defects in pathogen recognition. The assay involves a simple skin-prick test using pattern recognition receptor (PRR) agonists to trigger an observable inflammatory response in immunocompetent individuals. The authors suggest that this low-cost assay could be included in routine newborn screening to detect babies with IEIs before serious infections occur, benefiting therapeutic decisions and treatment strategies for patients with immune deficiencies. The authors seek collaboration with researchers to further evaluate and advance this diagnostic approach. [Extracted from the article]

It has become increasingly apparent that the biomechanical properties of neutrophils impact on their trafficking through the circulation and in particularly through the pulmonary capillary bed. The retention of polarized or shape‐changed neutrophils in the lungs was recently proposed to contribute to acute respiratory distress syndrome pathogenesis. Accordingly, this study tested the hypothesis that neutrophil priming is coupled to morpho‐rheological (MORE) changes capable of altering cell function. We employ real‐time deformability cytometry (RT‐DC), a recently developed, rapid, and sensitive way to assess the distribution of size, shape, and deformability of thousands of cells within seconds. During RT‐DC analysis, neutrophils can be easily identified within anticoagulated "whole blood" due to their unique granularity and size, thus avoiding the need for further isolation techniques, which affect biomechanical cell properties. Hence, RT‐DC is uniquely suited to describe the kinetics of MORE cell changes. We reveal that, following activation or priming, neutrophils undergo a short period of cell shrinking and stiffening, followed by a phase of cell expansion and softening. In some contexts, neutrophils ultimately recover their un‐primed mechanical phenotype. The mechanism(s) underlying changes in human neutrophil size are shown to be Na+/H+ antiport‐dependent and are predicted to have profound implications for neutrophil movement through the vascular system in health and disease. [ABSTRACT FROM AUTHOR]