Signal inhibitory receptor on leukocytes (SIRL)-1 and leukocyte- associated immunoglobulin-like receptor (LAIR)-1 regulate neutrophil function in infants

During severe respiratory syncytial virus (RSV) bronchiolitis there is a massive influx of activated neutrophils to the lungs. An exaggerated immune response contributes to lung damage and disease severity during RSV infection. We have previously shown that normal adult neutrophil function can be modulated by agonists of SIRL-1. Here we aimed to measure the potential of two immune checkpoints: SIRL-1 and LAIR-1, to regulate the function of fresh blood and sputum neutrophils from infants with and without severe RSV bronchiolitis. We show a modest inhibition of the oxidative burst through SIRL-1 and LAIR-1, in control and RSV-infected infants. In addition, SIRL-1 and LAIR-1 inhibited neutrophil extracellular traps (NET) formation by sputum neutrophils of RSV patients. Altogether our data show that inhibitory receptors LAIR-1 and SIRL-1 can be used to regulate neutrophil function. •Severe respiratory syncytial virus bronchiolitis (RSV) is characterised by a neutrophil influx to the lungs.•Circulating and airway neutrophils from severe RSV bronchiolitis patients show distinct expression of inhibitory receptors.•Neutrophil oxidative burst is regulated by inhibitory receptors in control and RSV infants.