Association of CD16hiCD62Llo Neutrophils with Disease Severity and Impact of SYK Inhibition in Sepsis.

BACKGROUND: Sepsis is a global health priority that leads to significant morbidity and mortality. Therefore, there is an urgent need to better understand sepsis pathogenesis to inform diagnosis, prognosis, and identify novel host-directed therapeutics. METHODS: Flow cytometry was performed on 35 sepsis patients and 18 healthy controls to characterize neutrophils and neutrophil subsets and their association with clinical outcomes. Additionally, purified neutrophils from 20 sepsis patients were stimulated with lipopolysaccharide (LPS), with and without R406 treatment, to assess changes in neutrophil populations and the impact of spleen tyrosine kinase (SYK) inhibition. RESULTS: We found that patients with sepsis have increased levels of circulating CD16hi/CD62Llo neutrophils that correlate with disease severity, including the need for intensive care unit admission, vasopressors, and mortality. This CD16hi/CD62Llo population expressed lower CD10 and CD62L and higher CD33 compared to healthy controls. Additionally, compared to healthy donors, the sepsis CD16hi/CD62Llo population had higher levels of SYK. Finally, ex vivo stimulation of sepsis neutrophils with LPS increased the percentage of CD16hi/CD62Llo population and the shift in this population could be prevented with SYK inhibition. CONCLUSION: These data suggest that CD16hi/CD62Llo neutrophils may contribute to sepsis pathogenesis and that SYK is a potential therapeutic target that can modulate this neutrophil population, but further mechanistic studies are warranted to establish a causal role in sepsis.