Low-Density Granulocytes Are Increased in Children with Acute Asthma and Associated with Disease Severity

Asthma is a worldwide problem. Many studies have found a close relationship between the occurrence and development of asthma and neutrophils. Recently, a subgroup of neutrophils called low-density granulocytes (LDGs) and the antimicrobial peptide LL-37 were found to be increased in many chronic inflammatory and autoimmune diseases. However, the clinical significance of LDGs and LL-37 in acute asthma attacks in children and their role in the pathogenesis of asthma remain unclear. Therefore, we measured the proportion of LDGs in peripheral blood leukocytes of children with acute asthma attacks and children who were healthy by flow cytometry and analyzed the expression of LL-37 by western blotting and RT-qPCR. To compare the difference in the LDG proportions in children with acute asthma attacks with respect to disease severity, the children were divided into non-severe and severe groups. Our results showed that, compared with the healthy control group, the levels of LDGs and LL-37 in children with acute asthma attacks were increased, and the LDG level was more significant in the severe group than in the non-severe group. The proportion of LDGs was positively correlated with the severity of asthma and neutrophil levels, but not with eosinophil levels. These results indicate that there is excessive activation of neutrophils in acute asthma attacks and heterogeneity in this cell population may be an important mechanism in the occurrence and development of asthma. Thus, LDGs are involved in acute asthma attacks in children and positively influence disease severity, and LL-37 may be an important inflammatory factor.